Suckers, indeed,
I bought the best one Gold-n-Sand makes. I am sure there are other quality vendors out there like DeserDog who posted here. I bought a small one at a prospecting Shop in Prescott AZ last summer because I left mine home. The supposedly reputable mfr. made a piece of JUNK! Also, in general, I have found the larger suckers of VERY limited utility for the prospector. The videos showing volumes of material being sucked are a joke. And worse very misleading.
The general concept IS APPEALING (as witnessed by the huge interest and sales) but the effort and awkward ergonomic aspects will kill you in short order - with very little to show for the effort. Lots of improvements, handles, valves, etc. have been suggested and executed - still it is a hard way to get nothing in my experience. I could be entirely wrong of course. Large bedrock cracks, especially underwater, would be a good application....but I rarely encounter one that can't be scooped out much more effectively. There must be thousands of these things laying around, unused.
On the other hand, the smaller bulb type suckers for bedrock work are of fantastic utility. Just my take, and remember I am no expert or have vast experience.
Thurman