SKIMMER PLUG POOL WINTERIZING TOOL:The Patented Skimmer Plug offers a simple yet revolutionary method for servicing and winterizing above ground and in ground pool skimmers.A first of its kind, the Skimmer Plug is far superior to any other skimmer closure or winterizing device on the market, being more affordable, as well as much easier to use. The Skimmer Plug fits all OEM skimmers without the need to replace the original skimmer faceplate.With no installation or tools required, the Skimmer Plug securely fits into the skimmer opening using our exclusive 3/4" thick Rovaseal thermo insulated layer that expands to plug and "grip" the faceplate, creating a 100% air/water-tight seal.Ice is no match for the Skimmer Plugs rigid outer plate, providing a durable and secure layer of protection through the winter. Made of UV and chemical resistant materials.HOW TO DETERMINE WHICH SKIMMER PLUG:Using the Skimmer Plug Model Sheet. (See picture) Determine your required model by first noting that you have an Above Ground or In-ground pool.Then see if you can find the skimmer make & model on the skimmer itself. Example: Hayward skimmers usually have the name and model embossed on the lip where the skimmer cover sits. Once you have found the correct make/model, that is the model SKU of the Skimmer plug you need. If this fails, measure the size of your skimmer, by measuring to the INSIDE of the skimmer opening. You might need to get in the pool to do this precisely.Then match your measurements with those on the Skimmer Plug Model Sheet to determine which model you need. HOW TO INSTALL:Dip the Skimmer Plug into the pool water before inserting into the skimmer face-plate; this will help the foam portion of the plug more easily slide into place. If pool water is not enough, use O-ring lubricant on all the edges of the foam pad. O-ring lubricant will also cure a minor drip caused by possible mold defects or nicks in your skimmers face-plate. Pack of 2.