Fingers crossed that if it's only a couple of millimetres over it'll get through OK.
Ignore the daft descriptions that eBay gives. Reading from the left, it's letter, large letter, small parcel, and the weight is a drop down below the daft descriptions.
It used to be so easy. eBay have made it so difficult.
The other thing to watch out for is that EVRi and Yodel are often the first options listed if it's a small parcel. You have to click to see more if you want Royal Mail. I made a mistake a couple of days ago, got a Yodel label. I don't even know where the Yodel parcel shop is. Had to void the label and start again. I just don't need this aggravation with labels.