The best hardline fitting ever made, period. The patent-pending Optimus gasket design is exponentially stronger than any o-ring design ever made. Our 1/8" (3.2mm) thick gasket provides huge surface area to clamp the hard tubing. With ultra-precision machining, extreme corrosion resistant Pro-XE nickel, plasticizer-free o-rings and super clean looks, Optimus fittings are so good we back them with a 10 year warranty. Hard line builds look amazing, but rigid fittings are a source of weakness and the #1 source of leaks and catastrophic failures. While o-rings are appropriate for G 1/4" threading, o-rings simply aren't able to provide the necessary holding force for rigid tubing. The Optimus patent-pending gasket design features a far higher surface area along the rigid tube, providing vastly stronger clamping force. With Optimus fittings, the hard tube is very difficult to pull out by hand, and virtually leak proof in typical liquid cooling builds. With over 50 years machining fittings and components for aerospace, medical, and heavy machinery (including the original lunar rover), Optimus fittings define new standards in PC water cooling. Fittings are the most critical but the least sexy of PC parts. But a loop is only as good as the lowest quality component. unfortunately, we found even the most expensive fittings on the market are substandard, not meeting G ?? spec and, worse, not even rated for water. HYPER ACCuRATE G 1/4? FITTINGS The highest end precision CNC lathes allow Optimus's thread accuracy down to achieve perfection down to 0.0002?, far beyond any other fitting available. And this is for the first and 1000th fitting, not just the first off the line. We constantly calibrate and double check our precision. After all, our aerospace and medical customers demand the best, so should liquid cooling.