Slug deterrent

In the Sunday Express today, there was a Suttons catalogue. Near the back was a thing called a slug collar, basically a ring of copper placed around the base of vulnerable plants. The price was prohibitive though at £24.00 for 6 of the 7" ones, and £19.00 for 6 of the 4" ones.
So I had a brilliant idea. Get some 8mm soft copper tube, cut into lengths of around 21" and find something to fit inside it. Then bend into a circle using the plug to join the ends together. There you have a much cheaper copper collar, of around 7" in diameter. (Sorry Suttons' Seeds)