Bully Extra - Heavy Oiled 1-Ply Leather Bully collars, leads and couplets are the most durable leather products on the market. Heavy oil treated leather with heavy duty hardware. There's nothing better than natural material that breathes with the conditions. The more it's used, the more comfortable it becomes. Large Dog Collars Designed for large dogs. Extra-long folds allowed around buckles. Feathered leather at buckle end provides a smooth backslide against dog's neck. Double construction sewn and riveted for strength.