ROTOR's first derailleur, the ROTOR Uno, was revolutionary in that it was hydraulic, but relatively conventional in that it was 11-speed and designed for use with a double chainwheel. It was widely admired but sold slowly.

But ROTOR were not disheartened. They responded by releasing the amazing, also hydraulic, ROTOR 1X13. Where the Uno was an 11-speed, the 1X13 was a 13-speed - the most sprockets of any derailleur in the world at the time (and, crucially, one more than a SRAM XX1 Eagle). Where the Uno was designed for a double chainset and was restricted to a 32T rear sprocket, the 1X13 was unrepentantly 'one by' and could handle a mere 52T (crucially, 2 teeth more than a SRAM XX1 Eagle). Where the Uno used a slant parallelogram, the 1X13 had a horizontal parallelogram and a wildly offset guide pulley (just like a SRAM XX1 Eagle). Where the Uno looked ultra modern, but discretely so, the 1X13 looked like something from a secret underground lab in Area 51, Nevada (and way, way, weirder than a SRAM XX1 Eagle).

And there were plenty of other neat touches. I particularly like the way that the pulley cage is split, so that, by pressing a lever, you can swing the tension pulley forward to ease wheel changes. Interestingly ROTOR's cylindrical indexing mechanism and split pulley cage are somewhat reminiscent of the Bridgestone SMS Max GT.

It's a fantastic object, but will it sell? I hope so, but I won't bet my pension pot on it.

This is an example of the, rather rare, black version. If you click the 'photos' tab and scroll down, you will see that this particuler derailleur was supplied with a bar end shifter, preferably for plugging int the end of your aero/time-trial bars.

• Derailleur brands: ROTOR
• Country: Spain
• Date of introduction: 2020
• Date of this example: unknown
• Model no.: unknown
• Weight: 376g
• Maximum cog: 52 teeth (based on the biggest cassette offered)
• Total capacity: at least 42 teeth (as widest cassette offered is a 10-52T)
• Pulley centre to centre: 103mm
• Index compatibility: 13 speed
• Chain width: 3/32”
• Logic: top normal
• B pivot: unsprung
• P pivot: sprung
• Materials: largely CNC aluminium with a some steel internal mechanical parts and a couple of plastic exterior covers