With over two decades of use, the original DT Swiss Star Ratchet system hasn't changed much and it’s always a great sign of quality when a brand keeps a system in place for 25 or more years. So DT Swiss found they could keep all the great traits of the original Star Ratchet system yet improve things like maintenance needs, durability, and reliability. Thus, the EXP system was created and it does all of those things. Maintenance has been simplified by having new end caps that do not require any tools to take off and even for most of the hub, you can service or swap your freehub without tools. The EXP system also improves durability in many ways. Bearings last longer as the ratchet system has been redesigned, allowing the bearing to rest into the inner ratchet ring that actually threads into the hub. Now the bearing stance is wider on the hub, which makes the bearing last longer and also improves stiffness on the hub axle. With the inner ratchet ring threading into the hub, it also eliminates a few moving parts from the previous Star Ratchet system, meaning fewer parts and less weight. Fewer parts to wear, fewer parts to replace, fewer parts to service...all of those add up to better durability and wear inside the hub. Durability also adds up to reliability in many ways, but one way the ratchet system works is the Star Ratchets make full contact, making it one of the most reliable drive systems on the market. Compare that to a pawl system where if all pawls engage (3,4 or 6 are most common), you only get a few millimeters of contact surface, whereas the full ratchet system makes contact, no slipping, no issues. Reliable as ever.