I think I posted a review of them, but I cannot find it at present.
The SGi510s are very nice though I sold the ukes I mounted them on for unrelated reasons. If you live in North America, I recommend ordering through Japarts in Canada. The main downsides to the SGI510s are the weight (they're closed geared tuners, so they are a touch heavy) and the difficulty of mounting (placing the holes for the small nubs that hold the tuners in place is difficulty; if you're doing a self-install, I'd recommend creating a guide for the purpose). I installed them on ukes I used for primarily outdoor ocean-side performances, and they excelled in that environment.