High-tensile strength, precision-made, carbon steel springs from Wolff help you achieve reliable cycling and top performance from both hunting and competition shotguns. Replace weakened springs for better performance or use as part of a custom project for ultimate reliability. Provides 20% extra power (XP) over factory original magazine spring. Measures 40" long and will fit all 3- to 5-round factory magazine tubes. Multi-Gauge XP Spring Pak includes two, extra power magazine tube springs for each of the following: .410 bore, 28 gauge, 20 gauge, 16 gauge, and 12 gauge 12 Gauge XP Spring Pak includes 10 extra power magazine springs for 12 gauge only. All springs may require gunsmith f Mfg: Wolff SPECS: High-tensile, heat-treated spring steel. Gunsmith fitting required for some springs as indicated.