This sponge features an extra fenestration which allows it to lay flat when wrapped around a drainage tube. Without it, the sponge will pucker , decreasing effectiveness by allowing fluids to pool around the drain tube. It's a simple feature that most other drain sponges do not offer. Includes all the benefits of non-woven Avant Gauze. Each 6-ply rayon/polyester sponge is highly absorbent, low-linting and fast wicking to wound beds.