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-32-087 - P-38 Lightning - late armament - .50 cal Brownings with covered cooling jackets & late 20mm cannon tips
AM-32-088 - P-38M Lightning - .50 cal Brownings and 20mm cannon tips with flash hiders