I've never heard of this "f1" brand, however, i bought my sachs oem clutch kit from gripforce-clutches, good transaction.
This includes a lightweight flywheel for 450$, that's a good deal. The lightweight flywheel is single mass, but i believe most aftermarket ones are.
I run a canadian HID kit company, if you have any questions about hid kits in canada or would like to check out our products please contact me here: http://absolutehid.ca
Hot: 2001 Estoril M Roadster
ZCP 19's michelin supersports, ZHP knob, JL 8W3
Cold: 2002 TiAg M3 6mt
ZCP 19's michelin supersports, deoranged, dechromed, led tails, ZHP knob, UUC SS v3, GROM, OEM 18's w310's,