About the PDI Barrel: PDI manufactures the highest grade quality steel inner barrels you can get on the market and they are famous for it. They are manufactured in Japan, The machining method for PDI Barrels is cold-hammer forging, which is the same process that real firearm barrels undergo. This process creates the best consistency for your bore. The machining tolerance for the inner barrel is +0.002mm, which means they offer the highest quality tolerance in the entire airsoft industry for inner barrels. PDI Barrels also have the best lapped inner bore surface quality for steel barrels on the market at ~20 microns. The steel material used is SUS304 Stainless Steel, which is the highest quality steel used for inner barrels on the airsoft market. PDI Barrels are also the straightest barrels on the market thanks to their superior machining. PDI Barrels also undergo strict quality control. In conclusion, PDI sought to make the best possible steel barrel on the airsoft conusmer market and suceeded. These barrels are highly reccomended and are personally used by our technicians. It is also recommended to add-on a lapping service for this barrel, which will give it an inner surface like EdGI.