.588" Barb for Booster Grommet (fits Grommet w/ 13/16" OD on Booster), 3/8" Hose Barb for Engine Vacuum, Black Anodized Finish, 3/8" Vacuum Fits Most Domestic & Import Engines. Earl's billet aluminum brake booster check valve replaces the OE (Original Equipment) plastic valve for a clean custom appearance. Choose from black or clear anodized finish & (3) vacuum hose options (3/8" hose barb, 1/2" hose barb, or -6 AN male flare). Fits most brake boosters or vacuum canisters w/ 13/16" port (inside diameter of the grommet on the brake booster).. This check valve is for use with naturally aspirated engines only (not for use w/ Turbocharged & Supercharged engines).