16 ga I think is about 1.5mm or thereabouts, it could be a little thicker, I only used 1.5mm because it was a offcut from a trailer I cut up & repaired, it seems to do the trick and I've had the seat on for bout a year with the missus as pillion for most of that time, I've had a few inquiries and am gonna make up a fibreglass mould, it'll save a lot of time if i've got to make a few
