I only bought two 5lb plates to use with a second-hand olympic dumbbell I purchased a while ago. These plates are wayyyyy better than the cheapo plates I've been using for years. They fit very well on the second-hand dumbbell, with a very small amount of wiggle/slop and if you have the Strength Co. dumbbell, these things are VERY tight. The tolerances on the plates for the dumbbell they are designed to work with are quite small and often get stuck when trying to pull them off. Does this matter? Well, sometimes it's a tad annoying but I think I'd rather have the plates fit so well that they don't move around then them fitting poorly. Yes, these plates are expensive but you get what you pay for and I'll most likely have these for many years to come. I will eventually be buying another dumbbell and the collars that work with them. Both the weights and dumbbell are much nicer that what I was using before. The collars are still weird to me, but they function like they should. The knurling is nice and the handle is thicker than the second-hand olympic dumbbell I was using previously which is nice. I tried using a Fat Gripz One (fits perfectly on my old dumbbell) with the dumbbell and it actually doesn't fit like it should aka isn't fully closed around the handle.