Blackhawk Serpa Sportster Paddle Holster, Gray, LH, Glock 20/21/37 - 413513BK-L.p The Blackhawk SERPA Sportster Left Hand Glock 20/21/37 is developed for civilian carry and range use, but it still has great patented SERPA design. It uses a traditional polymer material construction found in other injection molded holsters. It comes with a paddle mount only.