PART NO.  SPL.PAGE  DESCRIPTION                                                           
AHH5179   15.C.1    Piping -grille (46") -(cooling system)
AHH5179   15.R.18G  Grille piping (A/R) -(grille assembly)
AHH5179   16.C.2    Piping -grille -(cooling system, 1600)
AHH5179   15.R.18G  Grille piping -(grille assy, 1600 and 1600-MK-II)
AHH5179   TC.C.2    Piping -grille (46") -(grille assy, cooling system, Twin Cam)

Supplier Number	W	D	d
BMC AHH5179	0.358	0.136	0.103
Moss Motors 470-120	0.428	0.160	0.125

This grille piping is (originally) silver grey plastic, similar to the wing piping. It fits around the outer edge of the MGA grille surround between the grille and the painted car body. The smaller "d" bead fits inside hidden behind the grille surround. The larger "D" bead fits outside around the perimeter of the grille surround, so "D" it is the only part of the piping you see after assembly.

The Moss Motors piping is (as date of this writing) slightly larger all over compared to the original factory part. Not just that the outer bead is a bit fatter, but the center slot is also wider, so the piping fits a bit looser. This may leave a variable width visible space between the wide bead and the edge of the chrome grille surround.

The piping length "L" can vary depending on how you like the appearance. Aftermarket piping is commonly supplied with enough length to go all the way around the grille with the ends meeting in the middle at bottom. From the factory the piping was somewhat shorter, running a few inches inboard from the bottom corners to stop near the visible bottom rivets. As a matter of convenience, many people will trim the piping shorter yet to extend straight down the sides and stop about flush with the bottom of the body nose with no piping along the bottom of the grille surround.