Stainless Steel buckle with 3 grommets or Fused Holes, D-rings & Holder.
This can be modified for a custom fit, just fill in the measurement of how you want the collar to fit and I'll put the grommet right there, plus 1 more on each side of your measurement. I will also cut the end to appropriate length, so this choice will override you size pick.
I can also put 7 holes at 1" increments coinciding with the standard S, M, L sizing.
The last hole on all collars will be 3 3/4” from the end.
The easiest way to measure is with a soft tape measure around your dog's neck.