The OE wheel cylinders had much smaller diameter bleeders. On my 70 Chevy truck the bleeders are very close to the spindle. The extra diameter on these bleeders makes it so you can't get a socket or wrench on the bleeder once the wheel cylinder is installed. I had to disassemble everything, bleed the cylinder with a vacuum pump then reassemble. I won't be able to bleed it or flush the brake fluid in the future unless I once again disassemble everything, which I won't.