I’m using thicker or thinner fans, what size screw should I use?

Take the thickness of your fan and add 3-5 millimeters. 25mm fans use 30mm screws, 15mm fans use 20mm screws, and Phanteks’ new 30mm fans use 35mm screws. With 37mm fans, 40mm screws may work, but if they prove too short, you can go up to 45mm if you add washers to make up the extra 2-3 millimeters. When mounting fans to radiators through a thicker material, the same rule applies. Screws that are too long can cause damage to radiators.