What size reptile basic hide box for my bp?

Got my 20L tank pretty much all set just need the hides, what size hides should I order?

Depends on the size of the snake. My 420g girl seems to really love her large RBI hides. She sits on top of them at night and goes inside during the day. She also digs little tunnels under the aspen and makes her own "secret" ways into the hides ;)

I like my RBI hides also http://www.reptilebasics.com/hide-boxes

I have a young 140g female that squeezes snuggly into the small hides. Two of them are perfect for a 10gallon aquarium for baby snakes. I have a couple medium hides that will go into my new bigger cage that she'll move into in a couple weeks.