Xena XSU Lock - 18mm - Chrome Steel U-Bar XSU-310 XENA XSU locks pair the highest-quality materials with top-notch design for rugged build-quality that stays highly resistant to the elements through years of use. Constructed from high-grade stainless and inert gas-hardened steels, XSU69- 16mm Chrome Steel U-Bar XSU102- 18mm Chrome Steel U-Bar XSU310- 18mm Chrome Steel U-Bar