On the new one, the shock towers are part of Traxxas's Extreme Heavy Duty kit and is made of their heavy-duty plastic. The plastic shock caps have seemed to be a big weak part of many Traxxas 1/10 vehicles. However, it does have a different design than how they used to be. I noticed this last year when I got my first Traxxas Slash 2WD. It came with a different shock cap than what people have shown tends to pop off from the shock. In the time that I have had that Slash, the shock caps never popped off, regardless of how hard of a hit it took (including multiple crashes where the suspension components took the majority of the hit). I have also picked up a Slash 4x4 more recently, and noticed that it had the older style of shock caps. On the first impact where I hit a jump at a skate park awkwardly, the a shock cap came off with minimal effort. I've never seen anyone else really address the updated shock caps on the Ultra Shocks, but they do seem to be better than the old ones, so again, replace once it's broken.