Ring Height. Scope rings usually come in three sizes of low, medium, and high. The size of the objective lens on the scope does have some influence here.

Hawke® Optics has expanded its Tactical Scope Ring Mounts to include four new 34mm size options. ... These scope rings are made from high-grade aluminum that is anodized with a matte black finish.

My Winchester Model 70 Featherweight in 7x57 Mauser with a Weaver mount gave me fits. I removed the scope rings and discovered that the bases themselves were misaligned and pointed left.