The Rob Roberts Biz Raptor Invector Plus 20 Gauge Choke is crafted from high-quality 17-4 PH stainless steel offering exceptional durability and performance. Specifically designed for optimal use with bismuth shot this choke is a standout in the RRaptor Series. It reflects years of product development and technological innovation ensuring superior performance in the field. Note that this choke is designed for placement in one barrel only enhancing the precision and effectiveness of your shotgun.