Unfortunately, all bases, rings, and actions are not manufactured in perfect alignment with each other. Whether you have a one-piece or two-piece base, the odds are against you that your rings will be in perfect alignment. Why chance putting your scope in a bind, whether it is a $200 scope or a $1000+ scope? The Sinclair Scope Ring Lapping Tools are designed to correct the misalignment of scope rings. The Sinclair Scope Ring Lapping Tool is used to align the rings first and then to remove just enough metal from the scope ring bearing surface to fine tune the alignment. Misaligned rings actually cause your scope's main tube to bend, causing distortion and requiring you to use Mfg: Sinclair International