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.
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Hot: 2001 Estoril M RoadsterZCP 19's michelin supersports, ZHP knob, JL 8W3
Cold: 2002 TiAg M3 6mt
deoranged, dechromed, led tails, ZHP knob, UUC SS v3, GROM, OEM 18's w310's,
Fun: 2006 YZF-R6, black, ohlins, pazzo, graves