20 inch x 16 inch
This is the overall mounted size
This is a standard UK frame size, frames in this size can be easily bought from homeware shops.

20 inch x 10 inch
This is also a size that can be bought in some homeware shops such as The Range or Dunhelm Mill.

16 inch x 16 inch
The print area is usually 11 inch x 11 inch
This is also a standard UK size. I have bought frames for this size on the internet and in The Range etc