This is Atlantic Water Garden's Skimmer Mat Kit. We have a large selection of Filtration/Skimmer Replacement Parts and other water features from Atlantic Water Gardens.

Manufacturer's Description
When used in conjunction with the standard skimmer net and brush panel, Matala Mat Kits create three-stage mechanical filtration that reduces maintenance and extends the time between skimmer cleaning. Mat Kits fit all Pro Series Skimmers.