Haven't used bar muffs on a bike since the late 80s, not since heated grips became more readily available. However, this thread might give you some food for thought...

http://www.xt660.com/showthread.php?t=18436

On the Tenere I have had Oxford Hot Grips, which worked OK till the controls broke. Then I fitted Symtec grip heater pads, which were infinitely better...

http://www.windingroads.co.uk/shop/product.php/116/symtec-motorcycle-heated-grip

Now I swear by heated gloves and vest by Gerbings - not cheap, but I would not go back to heated grips again after experiencing the loveliness of heated clothing.

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