The first RRS lever clamp I had was B2-Pro way back in Jan. 03. A year later the clamp started to wear in the cam area which caused plates to start to slip. A call to RRS was answered by saying that they had made some improvements in design and to send my old one in for exchange. It looked like they changed the cam rate and Belleville washers. Now have RRS B2-Pro LR and B2 LR II RRS D2H L-plate 2005 RRS D200 L-Plate 2006 RRS 300mm foot 2006 KIRK 80-400mm collar and foot 2003 RRS D300 l-bracket RRS d700 L-bracket No problems with any of the above not holding in a clamped position.