I have a sprite (another on the way), and the bagua that china buye carries. I ended up getting a m4 (metric) bolt from lowes, and replacing the positive pin in the sprite. I had to shorten it to 11 mm to work for my batts, and this shortened the throw on the switch. This also shortened the distance that the switch button had to be unscrewed thus less chance that the switch button would come completely out and possibly get lost.
I had to do this because I tried to adjust the positive pin with a screw driver( from the top ). I broke a"tab" off of the top of the pin. Man, that sucker was tight! This caused the positive pin of the pro tank I was using to "tilt" over to the 510 connector part( of the pro tank base) when I tried to reconnect it. It shorted and got hot like zipflint said. I ended up using a 6 mm socket, and a hex key in the air flow hole (to hold it) to free it up. I also had to use a pair of pliers to hold the black plastic piece that the bolt was screwed into so I could finish getting the brass bolt out of it. I worked the new bolt in and out for a bit until it "broke in". Now I can adjust it with my fingers, and it works good. This was tedious, so use great care if you go this route. I had no choice, or I may have thought twice about doing this. One could end up messing up the plastic piece, and render the mod useless. The bolt I replaced it with is made of zinc, but it fires good. I've been using it for two weeks now every day, all day long with no problems. I'm looking for a brass m4 bolt, but not too worried about it.
I bought my "true Bagua clone" from Vapor tech on a preorder. I like it really well too. It has adjustable top firing pin, but it has a limited amount of adjustment. It likes shorter batteries (48 mm to 50 mm). Anything longer will leave a gap in the cap to tube. I noticed that when using the pro tank on the bagua it would "choke " the air flow a little when sitting flush. Not enough to not use it, but I ended up liking it best with an ego adapter and a Davide mini. I may like my device a little "airy" YMMV. The only problem I've had with it is I dropped it and broke the one of the magnets in the switch. I replaced it with a spring, and its going strong again.
Of the two, I prefer the sprite. It is better made with a "fine " machined thread as opposed to the "course" thread on the bagua. The sprite is also less "fiddly" with adjustment to the batteries after the "modding" I done. The airflow adjustment on the sprite is a plus too that I can dial in my pro tank to exactly the way I like it. I paid more for the sprite, but imo, for me, it was well worth the extra money.
One more thing about the sprite fire button was it was a little "crunchy" at first. I noticed that the machine marks where the brass fire button meets the stainless bottom cap was a little rough. I thought to smooth this up, but it worked itself out for me. Smooth now
