This ultra-light spring is made of stainless steel. It fits all 13XX, 22XX and Discovery valves. This is the lightest valve spring available in the industry. The length and diameter are just right that it fits all three valve types exceptionally well.
To pressurize Discovery models from empty the bolt needs to be pulled back one click or fully cocked. This also applies to bulk-fill 22XX.
13XX models will need to have the bolt pulled back one click or fully cocked before pumping or the valve will not seal. This spring will not fit if you are using a shortened valve-check. The light valve spring I have listed for Maximus and Marauder Pistol models will fit with a shortened check.