13mm upgrade spring for TM AWS - 450FPS (M135)

PDI air technology

is a Japanese manufacturer known in the airsoft world mainly for its cutting edge quality stainless steel barrels. These are some of the best (and at the same time most expensive) barrels, you can be buy. The company also offers upgrade parts, especially for sniper rifles - cylinders, hop-up chambers and buckings, trigger sets, the aforementioned stainless steel barrels and a cheaper range of carbon steel barrels. Yet the PDI main production area is the manufacturing of training equipment for the police, pepper cannons and pistols and paintball guns.