I had this built for a 2015 Vespa GTS - fitment should be good for Vespas with same seat pan layout (ABS models).
I’ll let the experts that made the seat describe it from an email exchange during the purchase process...
“X-Low GTS seat which is approximately 3" lower and we cut into the plastic seat pan to create a metal shelf. This metal shelf then protrudes into the under-seat storage compartment by about 2". The X-Low is more comfortable then the Low as we are able to add an inch of foam on top of the Closed Cell Foam. The raincover bin is removed. There is a "step" between rider and passenger area on the X-Low. The modified seat will not be any narrower as the seat pan width is dictated by the seat pan.”
If you need more pics just let me know.
Price is $275 shipped in the CONUS.