This listing is for eight (8) Elgin Industries 1/2 set valve lifters manufactured by Delphi for 2005-13 GM family models using the 5.3L or 6.0L V-8 engine with Active Fuel Management (AFM). P/N (4) HL-7011S + (4) HL-2148S. These AFM lifters are the 2nd Generation design. This is a half (1/2) set of valve lifters (enough for one bank) required for AFM V-8 engines (4-AFM; 4-non-AFM). These are the NEW DESIGN - 2nd Generation improved lifters. If he 8th digit (from left to right) in your VIN numbers is a B, C, J, L, M, P, T, Z, 0, 3, 4, for the 5.3L or 5, B, G, J, K, U, Y, for the 6.0L AND your engine has cylinder deactivation, these are the correct lifters. NOTE:AFM lifters fail due to a faulty VLOM (valley cover) - Updated VLOM# 12571609 from GM must be installed with new lifter to prevent future failures and warranty coverage.