dont know which Exxentric device is best for you?

dont know which Exxentric device is best for you?

16th May 2022

We know choosing between a kBox4, kPulley2, or LegExx can be tricky, but we are here to help you! Below, Fredrik Correa will take you through the selection process step by step. If you can’t find your answer here, you can click the button below and fill out the form and our product specialists will be happy to suggest the right solution for your needs.

Key takeaways:

  • Choose the kBox4 if you focus mainly on squats, deadlifts, i.e. vertical exercises.
  • Choose the kPulley2 if you focus mainly on rotations, pulls, i.e. horizontal and rotational exercises.
  • Choose the LegExx device for a superior leg extension exercise with a focus on the quads.
  • The main differences between kBoxes are platform size, number of flywheels, and the presence or lack of the kMeter feedback.
  1. kBox4 Active System: small kBox platform, two flywheels, no feedback system built-in (but kMeter ready).
  2. kBox4 Lite System: small platform but lighter than the kBox active, four flywheels, feedback system built-in.
  3. kBox4 Pro System: largest kBox platform, 4 flywheels (up to XL size), feedback system built-in.

Before we get into the details that differentiate one unit from the others, what unites them? All flywheel training devices rejoice of the same:

  • Premium quality
  • Stainless steel shafts
  • Auto-retract mechanism (for setting the drive belt length)
  • Same flywheels and accessories

Whichever you pick, a flywheel training device will be a great investment for your strength and health. Moreover, in case you change your mind, Exxentric has a 30-day customer satisfaction guarantee that allows you to return the unit for a full refund on the device or even get another unit. We’re only happy until you’re happy!

Why do you want to do strength training?

If you haven’t been training in a while or at all, if you are active in recreational sports and other activities that aren’t primarily strength-focused, then we consider your strength training to be complementary to your activity and a fairly beginner level. In this case, you probably want to involve the lower limb and focus on vertical exercises, which makes the kBox4 the perfect solution for you. The kPulley2 is for mainly horizontal exercises like pulls, rows, flyes, wood chops, etc., and is loved by many of our pitching and striking athletes (e.g, golfers, tennis, baseball, martial artists, etc.) If this sounds more like you, then the kPulley2 is the perfect solution. If you want to maximize your training results and are considering both units, check out our combo systems for medical, performance, and fitness.

kBox4 ActiveExxentric kBox4 Active

If your focus is vertical exercises, the kBox4 Active is the perfect starting point. Available in Anodic Bronze color, with the kBox4 Active you have a competent, entry-level unit. You can load two heavy flywheels (which is a serious amount of inertia) so if you’re planning to do training sessions of 8-15 reps, the kBox4 Active is perfect even for stronger physiques. If you want more inertia you can upgrade your kBox4 with our advanced flywheel knob and mount up to four flywheels, well enough inertia even for the most competitive powerlifters. The kBox4 Active is made of steel and is heavier.

The kMeter system is an electronic sensor that transmits training data to your smartphone so you can get instant feedback on your training.If you want to add it to your kBox4 Active and you’re not enthusiastic about the weight, we suggest adding it to your cart and we will mount it for you. If you can’t decide, don’t worry. You can buy it now and mount it yourself afterwards since it is quite easy to mount.

kBox4 LiteExxentric kBox4 Lite

If feedback is very important to you and you prioritize mobility then you should take a look at the kBox4 Lite. It weighs only 9 kgs and features a built-in kMeter. With the standard knob it can take up to four flywheels but with the advanced flywheel knob up to six. kBox4 Lite also comes in three colors, Jet Black, Midnight Blue, and Anodic Brown. This is the most common pick for users that need very high mobility like traveling athletes, trainers, or physios who are moving around a lot. Also, if you want the smallest footprint and lower price, kBox4 Lite is the answer.

kBox4 ProExxentric kBox4 Pro

Why the Pro? Mainly because it features the largest operating area of our kBoxes while offering the same benefits. Many can get excellent training on the smaller kBox4 platforms but the extra space can be really proficient to train on. More space means more freedom of movement and hence, better training results. In a clinical setting or in some sports teams, larger platforms can be necessary, in order to fit different people of different sizes, therefore the Pro becomes the obvious choice. You can also mount four flywheels up to the XL (extra large) size that only the Pro can handle, six with the Advanced Flywheel knob. Basically, with the Pro you don’t have to worry about limitations. It is built-in aluminum, and it is just as heavy as the Active, therefore still portable. The majority of our professional users’ coaches, personal trainers, clinicians, or military customers go for the Pro.

When and why the kPulley2?Exxentric kPulley2

The kPulley2 device needs to be mounted to a solid attaching point, generally a wall. It is basically a flywheel training device with a beam. On the beam, you have a sliding pulley that allows you to change the direction and the height you want to pull from. You can pull straight out, upwards, or downwards in different angles and do all types of exercises such as tricep press, bicep curl and row to wood chops, rotations, and even a bunch of great leg exercises. There is of course some overlapping with the kBox4 but for a maximal range of different exercises, combining the kBox4 and the kPulley2 is a great combo. The kPulley2 device comes in one version only but in different colors, the Jet Black and Midnight Blue.


The ultimate leg extension device, whose sole purpose is to target the quadriceps muscle. Built on the same scientifically-proven flywheel technology, it ensures maximized hypertrophy by providing 100% muscle stimulation in the quadriceps. With the same flywheel-feeling, the LegExx is perfect for those who never skip leg day.

If you still have any questions, click the button below and fill in the form and get free expert advice!

Which accessories do I need?

After you have finally decided on a unit, you will then realize there are tons of different accessories to choose from… but don’t worry! All accessories are available for the unit you pick and you can always order more accessories at a later stage. Our advice is that you start with what you need and add the items you want at a later stage. If you are still unclear about what you need, here is some explanation of our accessories and what they are good for.


Critical to use your flywheel device, whichever you pick: the flywheels. They come in different sizes and weights but the important thing about flywheels is the inertia. The only thing to keep in mind when choosing the flywheels is what range of inertia you need (from light to heavy) and how big steps you can take.

The range varies from 0.005 (XS) kgm^2 to 0.070 kgm^2 (XL). The more inertia you have the higher the potential for force development is, although, in the end, it depends only on how hard you pull. Starting with S (small), M (medium) and L (large) flywheels work for most people. With the S (small) flywheel you have a low inertia starting point and therefore you can do upper body or fast movements. You can also add all the flywheels for heavier exercises. If you want to do a lot of the heavier exercises like deadlifts and squats maybe adding one or two L (large) flywheels extra can be good. Adding more than one of the S (small) or M flywheels isn’t really beneficial since 2xS equals an M (Medium) and 2xM equal an L (large) flywheel.

Harness and Hip Belt

Both are designed to be connected to the kBox4 for vertical low limb actions like squats, split squats, calf raises, etc. The belt only loads from the waist down, which can be beneficial for those who have had previous back issues or can’t load from the shoulders down.

The harness allows you to use the hip extension more during squats movements, makes you perform better, and engages the glutes and the back more. If you are trying to produce a lot of force and power in the squat and improve this capacity maximally, the harness is a must. In other cases, it is a bit more open but we would say harness is standard if you intend to do a lot of lower limb squat-type exercises. The hip belt is an optimal choice if you want to unload your back.


Everybody needs a good Bar, as it is essential in flywheel training. With the kBar you can do tons of exercises like rows, curls, high pulls, deadlifts, and many front-loaded squat variations. Our kBar is super light, hence very pleasant to train with. Its lightness allows for all your energy to go into the flywheel instead of working against gravity for the maximal flywheel training effect. If you prefer an alternative to it, you might as well use a regular steel bar from a local store (or from an online store) that works just as well. If you have a 400+ lbs deadlift, investing in a long steel bar can be necessary.


Grips are great if you want to do single-arm exercises like single-arm rows but also great for some bilateral pulls in rows, high pulls, sumo deadlifts if you just want a V-shaped grip. Very comfortable and fairly inexpensive accessory. Exxentric recommended.

Ankle Cuffs

Wrap them around your ankles and use them in hip extension or leg curls, great exercises for posterior chain and glutes.

Foot Block

Allows you to set up the kBox4 for lateral movements (like lateral squats) to maximize glute training. Perfect for training for sports with the change of direction or skating type actions. Also great for a lot of sprint exercises like sprint start squats.

Decline Board

Combined tool for decline squats to target the quads (especially if used together with the hip belt) and calf training tool if you stand on the flat side. If you want quads and calves of steel or if you are doing rehab for achilles or patellar tendinopathy, this is your go-to accessory.

Elevation Block

The elevation block lets you stand elevated, which can be great for a really deep squat if you are short or super flexible. They can also be used to increase range of motion in deadlifts and other exercises or put the focus on one side, for example in squat training after ACL surgery. By elevating the non-injured side you will work more with the other side, the leg that needs more training.

Head Harness

Working the neck muscles? The head harness is designed just for that.

Accessory Racks

Does your home gym look messy and you want everything in perfect order? Then we have both wall-mounted and free-standing accessory racks to stow away your equipment.

Have more questions? Let our professional advisors help you!

Fill out the form below to get FREE professional suggestions tailored to your needs.

As always, your feedback is important so make sure to reach out!

Happy DOMS!

/Fredrik Correa, M.D., CEO

Follow @fredrik_correa 

Products In This Article