Check the listing for details. Vacuum Tube Vented Shock Proof OCTAL Socket Mounting Plate. Condition: New. Listed at 2.85 USD. Product is available NOW! This is a shock proofing thermal venting mounting plate for Top side of chassis. IT IS for use with OCTAL type TUBE Sockets.The image shown is for noval, but the only difference is the socket holes. All mounting holes and inset center hole are the same for all types. It can also be used with the anodized tube shields I offer. This item provides the following benefits to your chassis design: 1) the heat ring from the tube starts a chimney effect air flow drawing out hot thermal air from the chassis underside to prolong life of components and not have their values wander 2) the supplied gromets will help removing microphonic vibration picked up by the chassis and dampen it's transmission to the tube.3) In a non-obvious benefit, it also allows you to make all of the tube holes uniform, thereby allowing you to easily modify your amp for a different tube type in the future with no chassis mods. The holes are easy to make using a Greelee 2-1/4" Radio Chassis Punch #730. These are getting harder to find, but they are available from time to time. I got one recently for 60 bucks. You can also use a 2-1/4 Milwaukee bimetal hole saw. Best way is to use a piece of plywood to make a drilling jig so that the pilot is not needed. The jig can also have the 4 mtg holes in it, and then you can also array a line of holes into your jig so it is perfectly lined up and quick to cut in a drill press. That is actually easier than cutting the smaller holes and trying to get them to line up. As a style touch, use socket hex screws to mount the plate and socket to give a precision engineered look. Each plate comes with 4 rubber gromets for the mounting holes. 4-40 screws w/ flat washer is recommended is recommended. Some user assembly required. Hole required for plate inset to chassis: 2-1/4" (actual size, not "trade size"...beware "trade sizes" are larger than actual size. socket mounting screw centers are 1.1" (28 mm) ships from Texas USA I combine shipping across all items. It is automatic, if you want to see the postage, put the items in your cart, and go to checkout and you can see the itemized total. You can either then, proceed, decline or edit you cart directly. See my other listings for sockets, mounting plates for Octal, or 4 Pin for 300B or sockets and caps.