CRV stands for Chrome Vanadium Steel. This type of alloy is used in high grade hand tools.
The mechanical properties of CRV are much better than regular carbon steel and therefore tools made from CRV are much stronger and get worn out less quickly.
The retaining rings used in the Safewrench® are also of high-grade steel. Several heat treatments are needed to reach the perfect mechanical properties:
Both tool and retaining rings have a lifetime warranty. Normal wear is not covered by warranty.