Yes, the rubber is only on one side. Altogether it's a flimsy piece, made from what seems like a thicker sheet metal. Not a good design and solution. It doesn't sit deep enough to stay securely. You could fabricate it then glue rubber to it to replicate the original. Other than that, maybe adhesive window insulator? Not sure yet what I will do when getting to this. I have it original on my bike.
1982 Kawasaki KZ1300 A4
1981 Kawasaki KZ1300 A3
assembling engine, chassis & electrical from 79 - 89 parts