This little number was inspired by racers wanting an out of the way place to keep an active Spot beacon. It's also nice for other little stuff that you want close by hand. Loosen the bungee's and stash a wet rain jacket or leg warmers quickly underneath the pocket.
The Spocket has a tapered wedge shape towards the front so your butt does not hit it, or hit it less at least... VX 21 side panels provide structure and the 4 attachments are bartacked. Side cord length is fairly short so the ends don't fly around, but long enough to still shove something under it.
These attach to all our newer seat bags that have the 4 loops on the top panel and the front of either handlebar pocket.