The set includes turned brass barrels with drilled cooling jacket & early and late 20mm cannon tips.
It is very simple to use in Your model and makes it extremely realistic. Simply cut off the original plastic barrel and drill a hole in the remaining plastic parts and insert the metal barrel using Cyanoacrylate adhesives.
Other P-38 MASTER sets:
AM-48-023 - P-38 Lightning - late armament - .50 cal Brownings with covered cooling jackets & late 20mm cannon tips
AM-48-115 - P-38M Lightning - .50 cal Brownings and 20mm cannon tips with flash hiders