Found these batteries on Ebay and just wondered what the weight difference was going to be - I expected the Gel battery to be heavier than the standard Yuasa? battery for my 900ss but was quite surprised when I emailed the guy.....
"YB16 is 3.85kg, 12v12b4 is 2.4kg"
Here is a list of his Ebay items:
Westco Batteries I've had some weird dealings with a different Gel battery in the past but its turns out that might actually be the fault of my bike
Dunno anything about these otherwise.
Good luck - Frank