E Commerce site product description

Duplicate content is duplicate content, regardless of the type of website or type of page. There is no "penalty", per se, for having the same content as anyone else. It just isn't likely to rank well (if at all) when there are many other sites with that same exact information that have been around much longer than your pages have.

Generally speaking, we usually copy and paste the same old stuff everybody else has for product descriptions when we first add them to a website. Later, we go in and re-write them. We do this for two reasons:

1) We stand a better chance of ranking the page when its content is different than other pages for the same product.

2) We can always create a better description than the manufacturer has. Usually, they just have a brief blurb and bullet points. We turn each one of those bullet points into a sentence or two about the feature and the benefit that feature provides to the customer.

We'll also upload videos (if available) and instruction/installation guides if we can get our hands on them. This makes our pages more comprehensive and leads to better conversions when all of the information is there and people do not need to search elsewhere for it.

There is no set percentage for uniqueness. Make your pages as detailed as they can be and explain things from a customer's point of view. Do that, and your pages will undoubtedly be far more unique than every one else's.