Probe SRS Forged Pistons are designed for performance and race applications where a strong, lightweight forged piston is an advantage. With well over 200 part numbers now in stock for popular Chevrolet, Ford, Chrysler, and Import applications, these full-featured pistons are extremely popular for use in street and most racing combinations. Forged of 2618 t-61 Aluminum alloy for the ultimate strength and fatigue resistance. Light weight forging designs for quick revs and power. Tight piston to wall clearance design for better ring seal. Fully CNC machined domes and valve reliefs for perfect fit. Radial Anti Detonation Grooves reduce detonation by clipping pressure spikes. Pressure Equalization Channel enhances ring seal, making more power and increasing fuel economy. Full floated lightweight wrist pins and double spiro locks for durability. Narrow piston rings for the ultimate in power.Pit Stop USA offers Probe SB Chevy Flat Top Sportsman Race Series Piston Set - 4.155" Bore +4cc 12339-030 at low everyday prices. Be sure to check out all of our products from Probe Industries including Probe Industries Forged Pistons - Small Block Chevy.