A vacuum reserve canister captures an extra shot of vacuum from your engine for your power brakes. The COMP Cams Vacuum Canisters are for cars equipped with big cams and power brakes. COMP Cams Electric Pump Kit ensures your vacuum stays between 18" and 2". * Canisters double vacuum volume for power brakes * Recommended for vehicles with 14" of vacuum or less * Electric vacuum pump requires a 12V negative ground systems * Pump only operates when vacuum drops below 18" PartNumber : cca520-1 Description : Vacuum Canister Title : 5201 Vac Canister, Silver COMPVAC Plus California Proposition 65 : WARNING: This product contains a chemical known to the State of California to cause cancer, birth defects or other reproductive harm. Seal Outer Diameter : 0.575 Valve Guide Outer Diameter : 0.53 Valve Seal Type : Metal Body Viton Valve Stem Outer Diameter : 5/16 Valve Size : 5/16" / .530" Finish : Zin Plated & Polished Guide Size : .530" Engine Components::Valve Seals