With a knurled fore-end, you can leave your choke wrench at home, changing tubes in a field is easy. Available in Mid Range (out to 35 yards) and Extended Range (past 35 yards). HEVI-Choke choke tubes help you squeeze every bit of performance from your HEVI-Shot ammunition. 20 gauge tubes are available in extended range only. *WARNING- Extreme range choke tubes are not recommended for steel pellets larger than BB or excessive speed of more than 1550 fps. Use mid-range choke tube for those applications. Compatible with Optima Plus (Model 301 Extrema, Tekny's, Silver Pigeon II, III)With a knurled fore-end, you can leave your choke wrench at home, changing tubes in a field is easy. In ported versions, Hevi-Choke choke tubes help you squeeze every bit of performance from your Hevi-Shot ammunition.