The HK German factory intermediate poundage "satin" gray hammer spring is found in all 9mm, 40/10, and .556/223 burst trigger packs and has proven to be the most reliable and longest-lasting spring for burst trigger packs and trigger packs in general.Works in ALL burst packs and any Navy or SEF style trigger packs in the following calibers:
- 9mm
- 40/10
- 556/223