I own the JES, Size Genetics and X4 and while all are similar, the quality is seen in every inch of the X4. All the pieces look to be better produced and having used the JEs and SG for the last month, the difference when putting on the X4 is easily established and once strapped in the ride is much more aggressive. I bought the X4 Deluxe (Don't like gold) and added the 2100g springs, and the Quad attachment and girth base. This system is amazing! I am one to experiment with many various tools and this is by far the best out of all the ones I tested. This is an actual case of you get what you pay for and from the first time you start to assemble it, you'll know you bought a very quality device.