I've used these for 20 years, always deployed from depth using a reel. Last year I lost my DSMB and had to buy another, and I bought the DAN one at a show. I was very disappointed when I deployed it (from about 50ft) and saw that although it was fully inflated it just lay flat on the surface, and nothing I did to the line would make it stand up. I was depending on it to stand up as seas were heavy and I was some way from the boat, and I wanted to be seen.
Over the years I've tried and sold various ones of American manufacture, because my dive shop was in the Americas. None came close to what was needed, and most didn't survive more than a year or two of repeated use anyway. The one I lost I had owned for 15 years and it was still perfect, and was made by AP Valves (the Buddy brand) in England. I can't measure it as I don't have it any more, but it was very toughly made, around 5 feet long, something like 8-9 inches across when deflated, sealed with an over-pressure release valve, and providing ample buoyancy for two fully equipped technical divers to hang on. When deployed from depth it would stand upright and wave around as the load on the line varied with wave action, making it highly visible and prominent. Mine was solid orange/red, the correct colour for a normal ascent, and I also had a yellow one for when I wanted to signal an emergency. I see that they now make ones with orange on one side and yellow on the other, which is IMO totally crazy. But I believe they also now fit a reflective strip down the full length (as DAN do), which is extremely sensible. When I return to England shortly I must replace it, as they seem to be unique in the world.
They come with various inflation systems. The one I had simply had a wide neck with a non-release valve and you inflated it by purging a regulator. There are ones like the horrible OMS one I tried, which had a narrow mouthpiece for oral inflation. The DAN one has the same as well as a wide neck, and in fact is pretty well designed except that it doesn't stand up. For rebreather diving Buddy sell one that inflates from a charged cylinder, and they come in two sorts - ones that use a CO2 cylinder (Sparklets style) which are now useless for people who fly (because in many diving destinations they're not available, and when they are they're expensive), and ones that use a small cylinder you refill from your tank. The latter are pretty expensive, but I need two of them - orange and yellow. Plus two inflated from regulators.
A note on reels. I have lots of reels of different types for different purposes, but the one I like best for DSMB deployment is coincidentlly also made by Buddy. It's a sealed reel and line entanglement in normal usage is impossible. It also locks automatically once every reel revolution. That's all I use my Buddy Pocket Reel for, but for that use it's unmatched and I leave it permanently attached to the DSMB.
Footnote - does anyone with a DAN DSMB know how to rig it so that it does stand up on the surface when a load is applied to the line?