Unlike barcodes, you don't need to buy SKUs; just a few letters and numbers that are relevant to your product will do the trick. There is no guide maximum or guide minimum number of digits/letters in an SKU. It's very much down to you. Once you've settled on an SKU it's always worth googling it to check it doesn't have another meaning or have another product already attached to it. To give you an SKU example, for the products we make here at Notebook Love we use eg. 5NBL002. Please read the Seller’s Guide section where you will see where you can insert your SKUsOnce you are on the Seller's Guide page, click on 'Shop set-up', then scroll down to click on 'Product Listings', then scroll down to '1. Product Details' - then scroll down to "Inventory Details"