These barrels are to be used on the Italeri 1/35 S-100 Schnellboot kit released a few years back. These multi-part gun barrels assemble very easily, and make for a great upgrade to your kit. The 3.7cm gun is a combination of an machined aluminum barrel with brass detail parts. The barrel has a drilled muzzle, and the flared and perferated muzzle brake is a very fine creation. The skills shown on the 20mm barrels are just as impressive; as always, Master has another outstanding product.