Bleeder size

For my '69 300 with front drums. Want to replace the bleeder nipples, but need to know the size. Going to put in some 'speed bleeders'. Going to change out my rubber brake lines for some new ones. Old ones are cracked, making me nervous.

Speed bleeders make life so much easier when bleeding the brakes. Have them on my motorcycles, truck, and old 'Vett. I used to bleed the brakes for fun on the 'Vett...it's that easy lol.

So if anyone knows the size, please advise. Thanks!!
Author: GBsPanhead