Starting prime with ziploc bags

I sell industrial parts and have my own brand. So if I want to sell say, some nuts and bolts on Amazon prime, and I packed them in the plastic bag and write what size on the bag, can I do that? Or does a bag have to actually be printed with a brand and size on it? I pack every order like that on eBay and Amazon because every part is a different size.

3/4″ rubber washer Etc. I write the size with a marker normally.