To be clear, the QRs I am using fit into front and rear bases with a hole and the lever cams a slotted rod onto the pivot on the rings. The thumb lever is actually on the base, I was incorrect above about them being on the ring on my big bores. I have never used the ones that go onto a Weaver slotted type rail where the thumb lever is on the ring except on light rifles like 22rf, 22 250 etc and I have not evaluated them for return to zero.