F3 is short for Formula 3, and is a high-spec' (read "pretty bloody expensive"!) racing series where many modifications are allowed.

F3 NSR parts included braced frames and swing-arms, ignition/flywheel kits, ride height adjustable shocks, close ratio gear kits, etc., etc. Many parts were simply RS125/250 items, some direct replacements, some modified for the NSR. An HRC part number with "NKD" designation (i.e. 16020-NKD-970) denotes an HRC item designed specifically for the NSR, but other designations such as "NF5", "NX5", and "ND5" are ex-RS parts.

One exception to the rule (there's always one, isn't there?!) is where the MC18 rear suspension is concerned. Several people have been successful in fitting modified CBR600F3 shocks to the MC18 - notably those manufactured by Fox in the US.

Andy.
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