This is for TM HI-CAPA series & M1911A1
Made of SUS303 & with Variable Pitch.

Why does "PDI Recoil Spring HD Strong" do well in winter?
The original spring is the most poweful action included PDI's spring.So you'll get fun with the strong recoil,but when the spring be poweful,slide back action is really hard.As in winter,vaporised efficiency goes down,that spring makes the action bad.
So we developed an improved spring.This spring is a little down compared to original spring in power,but variable pitch conpensates the difernce.So you can get fun almost same recoil to original spring.
Besided,be a little softer,slide back improved well.Please check the below test result.

This test shows the high performance in bad condition.
We tested "how many times does HI-CAPA's slide stops available for 1 Mag"
The original Spring : 50 to 55,PDI Recoil Spring HD Strong : 65 around.
So you'll find it's easy to go back the slide.

If you want to install PDI METAL Chamber & Outer barrels,please use this spring.