This spring is intended to be used with 5" Government Model 1911s and 6" 1911s with our 6" Reverse Plugs / Spring Plugs.

Not recommended for use with Commander Models without removing multiple coils.

ISMI's proprietary design features enhance the spring's ability to hold the pistol in battery longer when fired to maximize energy dispersion and reduce sight movement. All ISMI Springs are made from silicone chrome instead of 150 year old music wire.

Every ISMI spring is heat treated, shot peened & stress relieved to enhance durability, consistency and reliability. ISMI is a contractor of the U.S. government and produces springs used in machine guns with incredibly high cycling rates. Also, the creator of ISMI springs obtained his knowledge from extensive research in the development of springs used in Indy car racing.

A note from the manufacturer: Maximum Service Temperature of ISMI's material goes up to 700 degrees. Music wire has a maximum service temperature of 250 degrees and can be negatively affected at temperatures as low as 175 degrees. This is important because temperatures approaching, or exceeding, the maximum service temperature are highly detrimental to spring life.

Exposure to maximum service temperatures promotes additional spring set and is detrimental to the relaxation of the spring. In other words, the spring will not decompress as rapidly as it should.

Available in 7, 8, 9, 10, 11, 12, 14, 16, 18, 20lbs.

In independent testing, ISMI spring have endured in excess of 100,000 compression cycles. We don’t recommend going that long between changes however. With an ISMI spring, practice routine maintenance and change it once a year.