Shim in bucket design, requires BC spring/retainer kit BC0950B. Made from aerospace grade, 4140 chromoly steel alloy and completely CNC machined from heat-treated billet round bar. Heavy-duty wall thickness eliminates distortion and cam face depression, while reducing overall weight from non-critical stress areas. Nitrided and polished to a surface hardness of 60RC for minimal wear. Provides lower friction with cam lobes and cylinder head lifter bores for improved durability.