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)Approved: Steel,Lead,Non-ToxType: ExtendedGauge: 12 GaugeConstriction Type: Mid-RangeConfiguration: Optima PlusFinish: BlackConstrictiondiameter: .718Chokes Included: 1Recommended For: 45 ydsMaterial: 17-4 Stainless SteelPorted: Yes