The bottom cap included with the skimmer directs outflow downward, which can disturb the substrate in shallow tanks. Swapping the bottom cap for this print redirects the skimmer's outflow forward (and to some extent, diagonally upward), allowing for use in shallow tanks.

The cap part is the same height as the original cap, but the outflow grille adds 7mm to the front of the skimmer. The tank pictured is 18cm/7in tall.