USA hot rod pistons to fit early 600cc 7-fin cylinders with late 79.3mm 650cc stroke. Attached diagram is useful ONLY for deck height to piston pin location, as these have a very high dome.
1959 Matchless G12 650cc NOS 72mm STANDARD bore Robbins piston one BARE SINGLE only WITHOUT PIN, clips, or rings (you must find your own). 
Brand new old stock.

Please ask any questions before buying. Thank you.

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I will combine your multiple purchases to try to save you money. 

No other parts here for these bikes except what is listed in my eBay store, but please watch for additional listings in the future.
Please choose your parts carefully. Thank you.

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Shipping for multiple purchases will be adjusted to your advantage. If you pay multiple charges, then I refund the excess to your PayPal account.

Payment as soon as possible, but certainly within 5 days. Thanks.

John McCoy owned Britalia Motors in Santa Cruz, California for 21 years before selling the retail franchise in 2002. The shop was originally established in 1946 with BSA and also sold Triumph, Norton, Rickman, Cheney, Moto Guzzi, Ducati, Cagiva, MV Agusta, Italjet, and Husqvarna over the years.

Sold the phones with the business and I am quite happy about that!