I have one bought for my +4 when it lived outside. I'll have to see if I have any info - I suspect the receipt was in the last 4/4 file when it went to a new home...
Lightweight, but definitely waterproof and full vehicle coverage.

Graham (G4FUJ)

Sold L44FOR 4/4 Giallo Fly
'09 Gen2 MINI Cooper ragtop
'90 LR 90 SW