Use this Corrugated Cardboard roll for the inserts in your fruit fly cultures. All you need is 12" to roll up and place inside culture. It is all I use in mine. The corrugated roll gives the maggots all the room they could possibly want to pupae on, it keeps them out of the moisture, soaks up extra moisture and they even go in between the corrugation making use of it too! Use in roach colonies, cricket rolls, ect.