Set of composite molded shock pistons for two shock absorbers with five 1.5mm holes & two 1.0mm holes. Two-way flow shock pistons work in different ways when the piston travels up or down. With the rubber valve installed on the piston, 2 holes are closed when piston travels up… then when the piston travels down, the valve opens 2 extra holes so the oil flows through 7 holes in total. This configuration allows for perfect landings from jumps, even with a soft shock set-up.Manufactured from specially-formulated Delrin composite material to provide smooth action & durability. Well-proven molding process ensures perfect piston roundness after production, so that the pistons move perfectly inside the shock bodies for identical shock action in all four shocks.