Features Nickel-plated high strength Carbon Steel 6.03mm diameter bore made to exact tolerances within 10 micron accuracy (+0.01mm) Square cut hopup window suitable for R-hop High polish with precision crown Made in Osaka, Japan Lambda's "SMART" line of inner barrels provide a precise and cost-effective solution for Airsofters who want to improve their gun's efficiency and accuracy without breaking the bank. Lambda "SMART" barrels are made from nickel-plated carbon steel, precision cut, crowned, and polished with 10-micron accuracy. Manufacturer: Lambda Specifications: Length: VariousInner Diameter / Bore: 6.03mm (+0.01mm)Material: Nickel-plated Carbon SteelCompatibility: For Tokyo Marui, Matrix, G&P, G&G, CYMA, APS, Krytac, ICS and other compatible Airsoft AEG Rifles