Motorized magnetic braking system. Digital adjustment of the resistance of the 16. Measurement of heart rate sensors to touch ear. Motorized magnetic braking system. Digital adjustment of the resistance of the 16. Measurement of heart rate sensors to touch ear. On-slip adjustable feet. Double ball bearings at every joint. Flank The life fitness x3 elliptical Company Makes six different models. They are the Life Fitness Elliptical X3, the Life Fitness Elliptical X3i, the Life Fitness Elliptical X5, the Life Fitness Elliptical X5i, Life Fitness X9i elliptical, and the Life Fitness Elliptical Sports Cardio SX30. These machines are at the upper end of the elliptical Life Fitness ellipticals are of the highest quality. The disadvantage of the Life Fitness ellipticals is the guarantee could be better for the price you pay. The last model mentioned the Life Fitness Sport Model gives you a lifetime warranty on the frame, two-year parts and one year on labor. All other models mentioned above have the same warranty, lifetime on frame, two-year parts and one year on labor. Life Fitness ellipticals X3, and X3i, are at the lower end of the six models. They are built very durable and are less than three thousand dollars. The X3i has four more programs than the X3 and is slightly better. The Life Fitness X5, and the Life Fitness X5i have something called the Select Stride, which means that you can choose from four different settings, sprint, run, jog, and walk. These ellipticals may last a lifetime, they are built very well. They are among the heaviest ellipticals made, so after they are put together, do not plan to move often. The Life Fitness X9i has eighteen programs and seven personal programs. The quality is said to be that of a commercial gym machine. This is one of the absolute best elliptical that money can buy. These ellipticals are quiet and very stable units. The latest model, the Life Fitness Elliptical Sports Cardio SX30 is at its lowest that the company is Firness Life. This is an average elliptical trainer at best and so if you are considering this model you may also want to check other competitive brands.