Hey!
Its the entry level model from Home Depot
VACUUM
Was around $150, but I already had the batteries etc.
It works well, we modified the tip to be a bit smaller so that it doesn't suck up larger rocks, we are going to make a custom tip for it with a screen to classify down a little smaller once again. We also shortened the hose so that we increased suction a little bit. It MURDERS batteries, that is the down side.
4 batteries might last 45mins? But if you find some good cracks / crevices its great.
We found it alot faster than "sweeping" and "scraping" up the gravels. We loosen them up with a prybar a nd then just vacuum away!