I use a Vacurect pump. It's a manual pump. It's a bit different from some other pumps in that the tension ring is used to form part of the seal and one doesn't need to
snap the ring onto your member (which some guys find uncomfortable). You just use the vacuum to pull the penis through the ring. The claim is that this helps with keeping scrotal tissue from being drawn into the tube (also uncomfortable). I can't say that it is perfect in this respect but it might still be better than other pumps (but I wouldn't know from personal experience).
Here is a YouTube video that shows how it works. Technically safe for work (the demonstrator's finger stands in -- so to speak -- for the organ being erected). I think they might want to re-think the music on the video. It's pretty but sooo sad...
youtu.be/4Hz8-V-1VZkThe product being demoed is the "prescript
ion" version. You can tell because, while it has exactly the same pump, it comes in a nice bag with twice as many tension rings and bigger bottles of both the water-based and silicone lubricants. Your insurance
may pay for the $500 device but you need to be careful about
in-network and out-of-network deductables and the like. Because it would have gone against my out-of-network deductable, my insurance would have "covered" it without paying a dime.
What I wound up buying is the consumer, over-the-counter version that consists of exactly the same pump with only five rings (spanning the same range of sizes) and smaller bottles of lube. It's, like, $195 and you pay for it yourself. Here is a video that talks about
some maintenance issues, including oiling the o-rings and taking the the device apart. Reassembling it is tricky even if you've watched the video.
youtu.be/zaZhKCaC5-sI can't compare this to other pumps. It works OK for me.