That depends on the breeding of the plummer or fell,I like a small 12"tts terrier for foxwork as most earths in cheshire are scratched out rabbit holes,it does'nt matter too much whether its a russell/ plummer or a fell/patt so long as it is able to freely manoevre to force the bolt by its speed of movement around the earth with steady baying,so long as you make a quiet approach to the earth most will bolt freely unaware of the danger of the waiting gun on top,its pressure from the terrier that will force it but if you're up a stop end then its a dig anyway and thats where I see the differen