We proudly use ISMI springs in all of our builds and component assemblies.  Over the years, we have spent a lot of time switching back and forth between spring manufacturers for our builds before finally making the decision to stick with ISMI.  The longevity and consistency of their springs has proven to be unmatched.
 
We personally use the 6# springs in our carry guns and found them to be our favorite for consistently igniting the primer, regardless of ammunition used.  For competition, we use the 4.5# without fear of light strikes.
 
Manufactured of Chrome Silicon alloy, these springs are designed to help tune the trigger pull of the Glock platform.