Duck Call Inserts for your hand turned duck call barrels. These inserts are made of bulletproof plastic called PolyCarbonate. Pre-Tuned American Made J-Frame Polycarbonate Duck Call Inserts. These Poly Timber Duck Call Inserts are designed quieter for best results with timber hunting. They are also an excellent option for people who are trying to get into the duck call making world to use in their barrels. They can also be used as replacement inserts for broken or lost PolyCarbonate calls, made from a hard bulletproof plastic resin known as PolyCarbonate. All inserts are pre-tuned before leaving the shop. Fit into a 5/8″ hole. You do not need our permission to make your barrels and use our inserts to sell them. We make them for the hobbyist or somebody who is wanting to get started in the duck call making world.