The cheap 6mm SF 5 for £20 something quid of ebay are excellent and the don't break very easily. I've only broke 1 and that was trying to cut that really hard resin impregenated MDF in 1 pass 13.5mm DOC @ 7mtr/min after it had cutt countless jobs in Ali as well has 1 pass 10mm DOC @ 5mtr thru same resin MDF. It was well shagged and had every right to give up the ghost. . . . . IMO they are spot on and worthy every penny.