Performance Hydraulic Roller Lifters: VThunder by COMP Cams, the leader in valve train Technology, introduces their new replacement Evolution Big Twin hydraulic Roller lifter to its line of V-Twin aftermarket products. Our new lifter features a rigid nodular cast iron body with a 52100 bearing, axle and wheel assembly for strength. VThunder's lifter utilizes an advanced ultra-high flow metering system which allows more oil movement through the engine to aid in cooling. Each lifter is precision ID Ground and matched with a Graded piston, and features a high performance retaining ring. (4) Performance replacement hydraulic Roller lifters for 1984-1999 Big Twin EVO