This is a round, tapered, plastic basket - used in a number of Astral in-ground skimmers.
Dimensions : 
Top Diameter: 8"
Bottom Diameter: 6"
Height: 4-13/16"
Distance between flat edges at top : 7-3/4"
Flat side length : 2-1/4"
Top lip width : 7/16"
Markings : 
"05280-0401" molded into bottom of basket
"05280-0402" molded into handle