These Intergrated Systems Management Inc. (ISMI) premium magazine springs are manufactured exclusively with certified aerospace specification chrome silicon alloy.
The springs are heat treated, shot peened and stress relieved after winding to enhance performance and durability. ISMI springs utilise the same design and manufacturing technology as used in IndyCar and Formula One racing. In a typical 500 mile race, a valve spring in an IndyCar will go through more than 2,500,000 compression cycles. Consideration of factors such as modulus, wire diameter, mean diameter, active coils, total deflection, spring relaxation, maximum service temperature, and operating environment; results in you having modern spring technology available for your pistol.
IMSI does not use music wire!
Music wire cannot be heat treated, shot peened and stress relieved after the spring is wound. Additionally, music wire lacks consistency from bulk lot to bulk lot. This results in inconsistent performance from spring to spring. This is the same technology that was in use 90 years ago when John Browning designed the 1911 style pistol.
ISMI believe that springs shouldn't be an ongoing worry or concern for the shooter. Springs should be an annual routine maintenance item. Change them once a year; go shoot and have fun.
If you have an STI crimped style magazine then the correct magazine spring is here:
ISMI 1911 / STI 2011 10 Round Magazine Spring
These springs are NOT compatible with the DAA 2011 38/40 Followers (GP254).