Here's a really handy accessory for tube amp builders. Use these and you won't have to drill a bunch of ventilation holes in your chassis. Nickel plated steel plate measures 2.522" X 2.522". Socket hole 1.413"/35.90mm, tube socket screw mounting centers 1.937"/49.21mm. Bottom mount 4 pin wafer tube socket 42112 fits this plate exactly. I'd powder coat these or use a hard catalyzed epoxy type paint like Sherwin Williams Polane.