I purchased this to replace a bearing on a supported rail. I read the website and searched everywhere and found this bearing was either 42 or 45mm long and it needed to replace a 42mm. Well it is 45mm so it doesn't fit the bearing block. I'm not sure why they do not sell a replacement bearing for a pre-assembled block. Seems wastefull to purchase a bearing and block when I already have a block that just needs a bearing. I am using it until I can find the correct bearing but it is not held in place by both snap rings as it should be. I would recommend to a friend unless this friend purchased bearing blocks.