I've only used Leupold and Burris, Burris I have never had to call customer service for. I did notice a crack in the clamp on my Leupold rings right where the 2 screws go thru. Possibly my fault usually is but it looks like a weak design. They did promptly send me 2 sets of wrong clamps and new screws I think they discontinued the ones I cracked so I gave up and bought another set. They were a bit different design but still not too rugged in the clamp.Leupold.