Word of caution - if you're going to use a 'bander', give a tetanus toxoid injection a couple of weeks prior to castration, or tetanus toxoid AND tetanus antitoxin(more expensive) at the time of band application.
I saw four nice 600-700 lb steers dying of tetanus last week, that had been castrated with one of those banders about two weeks earlier.
They had given a vaccine containing tetanus toxoid at the time of band application, but that's 'rolling the dice' - hoping that the animals will have time to respond to the toxoid and make antibodies BEFORE the tetanus organisms get a chance to grow and produce tetanus toxin. They lost the bet.