Forward Controls Design Flash Hider 9mm Luger 1/2x28 Nitride Black 9mm 1/2 x 28. At 2.063in long it's tiny compared to the 6315KM (2.4in). Like 6315 on which it's based 6315KM-S has asymmetric ports to optimize muzzle rise compensation without creating obnoxious concussion and noise its 3 and 9 o'clock ports are slightly smaller and shorter the design forces more gas to be vented through the 3 upward facing ports. Specifications for Forward Controls Design 6315-S Flash Hider: Manufacturer: Forward Controls Design Color: Black Finish: Nitride Fabric/Material: 4140 Steel Threads per Inch: 1/2x28 Length: 2.063 in Weight: 3.53 oz Package Contents: Forward Controls Design 6315-S Flash Hider Single use packet of Rocksett Forward Controls Design 6315KM-S 9mm 1/2 x 28: 6315-S Flash Hider 9mm Luger 1/2x28 Nitride Black