* 40-Series Represents the Perfect Balance of Performance, Durability and Value* Internally Contoured 6061-T6 Aluminum Cups and Cover* Innovative Clip-Seal Seals the Top Assembly and Captures the Compression Ring* Interlok Spacer Compatible* Sealed Black Oxide Steel Cartridge Bearing* Consistent Stack Heights Across 10, 40 and 110-Series* Internal Parts Are Cross-Compatible Across 10, 40 and 110-Series