I have just received two packs of these http://www.ebay.co.uk/itm/162257842548?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
I have previously bought some which were just two pieces of sandpaper (not very good) stuck tp card. These are like the sanding sticks that some model shops/sites sell being a sandwich of plastic foam and the abrasive. I have in the past paid £5 or £6 for these, whereas these are only £1.40 for 10 INCLUDING postage. I have tried them on plastic and wood and they seem pretty long lating.