GM LS engine owners and mechanics, these SCITOO lifter guide trays are exactly what you need when you're doing valvetrain work on your engine. This 4-pack fits a huge range of GM vehicles including Chevy Silverado, Tahoe, Corvette, Camaro, Cadillac CTS and Escalade, GMC Sierra and Yukon, and many more from 1999-2013 model years. They're compatible with Gen III blocks (LS1, LS6), Gen IV (LS2, LS3, LS7, LSA, LS9), and even Gen V blocks (LT1, L86, L83, LT4). The trays reference OE numbers 12595365, 12551162, and 12569259, so you know they're the correct fitment. What's really useful is that you can use these to convert Active Fuel Management (AFM) or Displacement on Demand (DOD) engines to standard lifters - though you'll need to switch to conventional LSx lifters since these trays won't work with the AFM/DOD lifters themselves. The construction feels quality and precise, ensuring proper lifter alignment and operation once installed. Whether you're rebuilding an engine, fixing lifter issues, or doing performance upgrades, having the correct guide trays is crucial for proper valvetrain function. The price is reasonable compared to OEM parts, and having a full set of 4 means you can do a complete job without hunting for additional pieces. Always double-check your specific vehicle compatibility before ordering, but for most LS engine applications, these trays deliver the fit and function you need at a much better price than dealership parts.