This universal float switch holder can be used with most protein skimmers. It's made from PVC and designed to work with Madison Sub Miniature Float Switch Model 3326 with a 3/8" thread. We recommend a Normally Open Float Switch. Float Switches are sold separately. Simply slip the float switch wires through the holder. Screw the float switch into the mount. Remove the bushing from the top of the float switch stem and slip the switch holder through the vent hole on the skimmer. Then replace the bushing to hold it in place. A drop of silicone can be used inside the vent hole to permanently affix the holder in the lid but that is optional. The switch can be adjusted up and down and the mount can be rotated to clear the side of the collection cup.