The S&J Hardware M14 Op Rod Spring Guide is has a lifetime warranty, if it ever fails under any conditions S&J Hardware will exchange it.
This Controlled Gas Nitride finish adds a sub surface hardness that far exceeds others that are on the market, while not making the core metal brittle. The the gray teflon finish has self lubricating properties, but only 4 microns thick so it will not add to the overall dimensions.
Unlike stainless steel you will not get the galling and binding after time that is so common with stainless steel used in this kind of product. Has been rated by the public as one of the best if not the best fit on a Norinco spring.