Gobi 4 Footprint
Fits well and protects the tent base. We pitched on a sodden (ducks were swimming on it, seriously) field for Easter weekend. When we left the tent was clean and dry, making it so much easier to pack away. Also a great guide to layig out the tent and getting a flat spot, rather than moving a half pitched tent about.
If only it was actually decent quality, don't regret buying, just expect to be buying it again in a couple of years time.