I purchased this product for the cheapest available price from a 3rd party seller called EasyDigi and the product that they sent me was counterfeit.
When the product arrived it was un-boxed and with none of the official documentation which immediately seemed suspicious. I would have forgiven this due to the discount price but on close inspection of the goods, and comparison with my current (and definitely genuine) Nintendo nunchuk, I concluded that the product was counterfeit. There were several differences between the products including the quality of the moulding/plastic, differences in the appearance of text and Nintendo logo and differences in the base of the connector cable to name but a few. I immediately contacted the seller and requested a refund so did not test the product, but one can only assume that if it's dodgy on the outside, the electronics on the inside are probably dodgy too.
So here's a WARNING:
Be careful when purchasing from 3rd part sellers, I wrongly assumed that they would all be checked by Amazon and reputable, but that is clearly not the case. Also, do not put up with sub-standard counterfeit tat, it is illegal and helps to support all other kinds of organised crime.
If anyones wondering, I replaced my order, buying from Amazon direct (at a slightly higher price). The item has not arrived yet but I fully expect it to be the real deal!