Hi Guys, If your talking about the Industry brand QB36-2, also the Tech Force 99, same rifle. The E9870 from Jim Maccari fits and works very well.The spring guide is .475" and the inside diam. of the spring is .480" I rounded off the square edges on the end of the spring guide, so they don't catch when You cock the gun. Just put 2 polished and moly greased washers on the bottom of the guide to reduce the spring tourqe, it's only about 1/8 " of spacer.and some grease on the guide. Even though this spring is a couple of inches shorter than the stock spring. I did not add any spacers, did not want to stress the stock plastic spring guide. It is definately a more robust spring. I could tell by the force I had to exert on my spring compressor. I did penetration tests into a phone book, to compare with my RWS 48 and my Industry B-3 and I figure It's shooting a .22 cal. around 700 f.p.s. all my rifles are .22
