SB/BB Chevy - 15˚ 15 Degree angle swiveling water neck for small blockand big block GM engines. Billet Specialties thermostat housings are precision machined from 6061-T6 billet aluminum and polished to a mirror finish. Fits small and big block Chevrolet® engines. Product Features - Dual Buna N® O-rings for a positive seal eliminating the need for a gasket or sealant - Swivels for proper hose angle - Stainless steel mounting hardware included