The Thread-on SD Housings are compatible with the patented FastBack® Direct Pullback System. These housings are heat-treated with chrome-nickel-moly alloy steel just as our bolt-on transmitter housings. The Box by box design provides unmatched versatility and value so you can use your Eagle Claw SD, Iron Fist or bolt-on blades (using a bit body) with one housing. The stainless steel timing mechanism makes clocking the transmitter to the bit a cinch. The straight-through gun-drilled fluid ports make the transmitter housing easy to clean.