Hello KF builders

In the catalog from skystar they use 2 gallon polybrush into the covering kit.
I have recently received the catalog from Polyfiber and they say You need for a J-3 cub 10 gallon plybrush and 11 gallon polyspray.

What I need for my KF 4, is a J-3 cub so much bigger?

I need to order the right quantity in once because i don't have a suplier in my region.

Thank You