These lids are primarily used for probing a circuit card from the top and bottom side. The lid is vacuum actuated, and has a separate internal vacuum cavity that aligns to guide pins installed into the probe plate. The lid floats inside an outer frame that attaches to the fixture. This allows the floating cavity to align without any undue forces placed upon it by the gas springs that hold the frame up. This provides improved targeting, as well as consistent, long term targeting accuracy. We offer many sizes for Agilent, Teradyne, and functional applications as well.