Even if you measure 300mm of clearance and a graphics card says it's 300mm long, it may be too snug a fit. We recommend giving yourself some wiggle room as well.

A tight fit at the back of your GPU could make it impossible to connect the power cables. Most cards have them on the top, but some (eg, Nvidia's RTX 2060 Founders Edition) have them on the back.

Also pay attention to where the PEG connectors are located on whatever GPU you purchase. It doesn't matter if it's drive bays, fans, or the front of the case - just measure near your primary PCIe x16 slot (the one closest to the CPU cooler), as that's where your graphics card should go. To determine how long your graphics card can be, measure from the expansion slots on your case to whatever part is most likely to obstruct the graphics card on the other end. We recommend going old-school and using a ruler or measuring tape - it will likely take less time and give you more accurate information. For pre-built PCs, you probably won't have it or be able to find the information online. Also, the test didn't crash, so I'm pretty sure it's working.To find out how big your GPU can be, you could try looking at your case manual, assuming you have that. Well here are my results when running GFXBench Metal from the App Store, so I'm assuming it's running. Tyler 942 0.0 0.1 2483100 6304 ? Ss Wed12PM 0:00.05 /System/Library/Frameworks/amework/Versions/A/XPCServices/MTLCompilerService.xpc/Contents/MacOS/MTLCompilerService Tyler 1520 0.0 0.1 2487196 8120 ? Ss 9:51AM 0:00.05 /System/Library/Frameworks/amework/Versions/A/XPCServices/MTLCompilerService.xpc/Contents/MacOS/MTLCompilerService Tyler 1655 0.0 0.2 2498324 15012 ? Ss 1:27PM 0:00.15 /System/Library/Frameworks/amework/Versions/A/XPCServices/MTLCompilerService.xpc/Contents/MacOS/MTLCompilerService Tyler 1777 0.0 0.1 2485672 9900 ? Us 2:10PM 0:00.04 /System/Library/Frameworks/amework/Versions/A/XPCServices/MTLCompilerService.xpc/Contents/MacOS/MTLCompilerService Tyler 1814 0.0 0.3 2502804 21948 ? Ss 2:14PM 0:00.26 /System/Library/Frameworks/amework/Versions/A/XPCServices/MTLCompilerService.xpc/Contents/MacOS/MTLCompilerService Building a CustoMac Hackintosh: Buyer's Guide

Metal compatible video cards