Which tank fits a 2012 ZX-6R?

Both list 2009-2012 ZX-6R fitment. The Arashi B also names the ZX636, so it covers more variants on paper.

Does either come with a cap?

The Arashi B listing says a cap is included. The Kawasaki A listing does not mention a cap, so assume you reuse your stock one.

Is the Kawasaki tank worth more than the Arashi?

Only if the OEM name matters to you or the price gap is small. No prices were given here, so check current store prices on both.

Will the Arashi tank fit a ZX636?

Yes, the listing states compatibility with the ZX636 for 2009-2012. The Kawasaki A listing does not name the ZX636.

Are these the same part?

They serve the same job, the coolant overflow reservoir, but they are different brands and the Arashi includes a cap. Treat them as alternatives, not identical parts.

Neither listing gives material or warranty details, so longevity can't be compared from the specs. OEM plastic is the safer bet for long-term fit.

Radiator Reservior Water Coolant Tank Bottle for Kawasaki Ninja ZX-6R 2009-2012 vs Radiator Water Coolant Reservoir Overflow Tank w/Cap Compatible with Kawasaki Ninja ZX-6R ZX6R ZX636 2009-2012

Both are coolant overflow tanks for the 2009-2012 Ninja ZX-6R, so the choice comes down to fitment confidence and what comes in the box. The Arashi B tank includes a cap and explicitly lists the ZX636 (636cc) fitment; the Kawasaki A tank is listed by year, make and model only. No prices were provided for either, so compare live store prices before buying.

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