I have a 7" long one of those that I got from Tanks, Inc.
The version I ended up with only had 8 steps, which made for really chunky needle movement. I probably would have been ok with 9 steps (one for each 1/8 tank plus empty), but Ibwas not happy with the sweep and replaced it.
I agree that the fully sealed/magnetic design looks solid and should work great for someone who is of with the number of steps it has.
