Very good value for money. These will cut a wide variety of materials from soft wood to hard ceramic tiles. Under hard use the disk gets hot and the plastic washers around the mounting screw go soft and the disk slips - therefore just dont bother using the washers or replace with steel ones. I find that for cutting ferrous metals standard nylon reinforced cutting disks are significantly quicker and generate less heat then these ones. However, these are a useful addition to your tool kit. As someone else wrote, a larger diameter disk would be useful for deeper cuts.
ADDED 6 MONTHS LATER: Still impressed with these. Good for cutting a wide variety of plastics without causing significant melting around the cut, unlike the mini circular saws I used to use. A bargain at this price!