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. Attractive matte finished aluminum plate measures 2.677" X 2.677". Socket hole 1.064"/27.03mm, tube socket screw mounting centers 1.433"/36.40mm (most socket with an enlongated mounting slot will work with this dimension...). We have a number of good 8 pin octal top mount sockets and at least one ceramic bottom mount socket (Angela Part Number 81003) on the Angela Instruments website that fit this plate very nicely; just check the dimensions and choose the one that fits your price point and performance standards. Please note that these plates are fabricated on automatic machinery with not a lot of attention lavished on an elegant finish. There are typically some small scratches and marks in the matte finish.The bottom line? These plates look good enough for most D.I.Y. tube amp projects but if you're really fussy you may want to make your own plates.