I bought some good ones (dronco I think), I cant get on with them and just use traditional type and backing pads as I think when used correctly they work out better in terms of money. Sure I know the sellers claim differently but its just not what I found and grit for grit they loose bite
Very true, most new flap disks are great for the first 5 or so minutes and then loose bite and the temptation is to put on another new one=£10+/hr on disks! Try to use a standard grinding disk and abrasive disks on backing pads, save (my favourite Klingspor) flap disks for special jobs and finishing.
Another vote for Klingspor, they last quite well compared to other discs I've used.