The Harmony High Volume Bilge Pump moves more water with less fatigue. Shortened length makes for less fatiguing strokes while more efficient design moves lots of water. Low-profile exit port won't snag on deck rigging.
Harmony High Volume Bilge Pump worked well - luckily, didn't need it for my kayak, nor my friend's, but others used it a couple times. Would be nice to have a loop or eyehole of some sort, to attach it to the kayak top.