Good used motorcycle seat of unknown origin.
It's likely a passenger seat for a cruiser style bike given the bolt hole placement and general appearance.
One small tear on the left side near the bottom edge.
16 1/2" Front to Back
12 3/4" at Widest point
3 1/4" rise from level ground to rear mounting tab
1 3/4" rise from level ground to front mounting scoop
1 1 8" deep front mounting scoop
12 7/8" from leading edge of front mounting scoop to rear mounting tab on center