the dogs of blackstaffs are cracking specimans,but they are of bigland boy[whippet greyhound]the smaller type f1 not many topping 20 inch, thin skin,heavy muscle on light bones may have the minerals for smashing cover as mine do,but these dogs can not do 3 or 4 days back to back when there is cover around.a pedigree bullxwhippet would have all on catching rats in a barn as neither dogs in the makeup are fast enough to catch much.the bull mine is out of is a working import