I've bought these before and they work great. I haven't used the ones I've just received yet, but they seem to be the same as the ones I got in the past.
Fantastic springs. Fantastic deal. Why buy one when you can buy 5!
Arrived several days early, just in time for christmas! Took some work to cut, but the spring works great in my nite finder, giving it a huge power increase. If you do not have a good pair of bolt cutters, I would strongly recommend the cut-to-length version, as this stuff is too tough to get through with regular snips.
Used it to mod my kronos and bug a salt gun. Increased the power and range on both. Highly recommended.
K26 Spring 11" with square ends (BETTER than McMaster)