Ever feel like you need a third hand to get everything lined up and back in place when you’re trying to replace a wheel, only to have a spacer fall out and roll directly into the path of a passing street sweeper? Here’s one thing that may not work on all bikes, but definitely works on many of them, including the last-generation ZX-6R this rear wheel belongs to. Often you can remove the oil seal (the black rubber ring), and flip the spacer so that the collar goes toward the inside. Replacing the seal on top of the collar then holds the spacer in place, i.e., “captures” it, while maintaining the same overall width. Measure to make sure that’s the case if there’s a shadow of a doubt!