Brake caliper question

["Phillips, Frank" <fwp@ufl.edu>]

Looks like I've done it now... A few weeks ago I bought a pair of rebuilt
brake calipers from my local NAPA store and returned the old ones as cores.
Tonight I got my front-end to the point of installing the calipers only to
discover a big problem, no plugs! Did not know I needed to keep the old
ones, did not know they were there. Anyway, what is this plug and can it be
found local at a typical parts house? Seems it's always something!!!

Frank Phillips
1968 MGB