There are five models to choose from. Each model has a specific purpose. 
The Kid's model is smaller and is designed for beginners. It only tilts from side to side, and has a lower height, making it easy to use. This model is the perfect addition to one of the other boards if your little one wants to join you in balance training. A tip for accommodating ultra-beginners is to place a book underneath each side of the board, which serves to restrict the lateral range of motion of the tilt. Doing this essentially adds 'training wheels' to the board, and gives you total control over how far the board can tilt. This model has a user weight limit of 55 pounds.
All of the boards have durable EVA foam which wraps around the ends onto the bottom. The reason i make them like this is to provide a good contact point with the floor so the board does not slide when one side touches the floor. This makes getting on and off easy and safe, and gives it a secure resting point if you lose your balance.
The Office model is kind of like the new and improved desk chair. Standing desks are growing in popularity because people are realizing that sitting down all day isn't the greatest thing to do. Unfortunately, it's pretty easy to stand in a lazy and damaging way, especially when a person is focused on working. That's why i made the Office model balance board! This design only tilts from side to side, and has a nice gradual arc that provides a good range of motion without being too dramatic. It requires the perfect amount of concentration to use while working, with the goal being to subconsciously make you stand up straight and engage your core while standing.
Next in line is the SUP Trainer model, which has the same side to side tilt as The Office model, but with a more aggressive slope of the arc. This board sits up higher, has a wider range of motion, and takes more concentration and effort to use. It wakes up more muscles and tendons, and it is recommended that you pay attention when getting used to this board. 
The Office and SUP Trainer models have a user weight limit of 225 pounds.
The X Boards introduce a whole other dimension to the mix. These boards articulate from side to side and also from front to back, making a much more wobbly surface that will engage a lot of the muscles and tendons from your feet all the way up to your ears. In addition to the four point range of these boards, they also swivel, meaning they can rotate like a merry go round. This is super fun and also uses a lot of the core muscles in your sides and tummy. To take all these features up a notch, the X Board Pro is only for the most balanced and advanced users. This board is steep and aggressive, and it will wake up muscles you didn't know you had. Please try another board first unless you are an advanced user. The X boards have a user weight limit of 200 pounds.