It's designed to fit the end of a large trofast tray (Approx 27cm x 19cm) 

It comes in two layers, a solid 3mm base (with holes for wooden scoop (not included) and a hollow 6mm layer, which you simply glue onto the base if you wanted (You dont need to glue it as it will sit snug when in the tray when in place) 

Perfect for sand, pom poms and rice play 
The pom poms in the photo are the mini 10mm ones and they fit perfectly 

They are not included