Muller Chokes currently manufactures chokes for Perazzi Generation IV barrels in 18.4 and 18.7 bore diameters. If you are unsure of whether your Perazzi is an 18.4 or 18.7 bore, you can find out by checking your barrel. Perazzi barrels are stamped with 18.4 or 18.7 under the forend, near the receiver. Finding this stamp will help you to select the right choke when ordering. If you still have the factory chokes, they also are stamped with the bore size.All Rights Reserved