Rail and Stile Set with Adjustable Slot

Have you ever slid a piece of 1/4-in. plywood into a 1/4-in. groove?
It ain't pretty. It's a fact of life that plywood is undersized in
thickness and this results in ugly gaps in doors with plywood panels.
So here's the skinny—skinny bit, that is. With Amana Tools' new
In-Stile and Rail System router bit set for $155, you can match the
size of the groove to the exact size of the plywood. This allows easily
custom fitting the groove to the panel. The set works for undersized
1/4-in. and 1/2-in. plywood in rail and stile material from 3/4 in. to
1-1/4 in. thick.
Each two-piece matched set works like a stackable dado.
It comes with a variety of shims, spacers and cutters that allow making
grooves (and the matching tongues) in two size ranges: from 0.197 in.
to 0.272 in. (approximately 3/16 in. to 9/32 in.) and 0.433 in. to
0.523 in. (approximately 7/16 in. to 17/32 in.). It takes test cuts and
trial and error to get the bit set up right, depending on your panel
material's thickness, but instructions from Amana simplify the process.
When you've found the perfect setup, using the bits is no different
from using any other matched bit set. Sets are available in three
profiles: ogee, bead and concave (pictured). All have 1/2-in. shanks
and produce a 3/8-in.-long tongue. The price of each set is slightly
higher than prices for matched sets that don't allow customizing the
groove size.

Source
Amana Tools, (800) 445-0077, www.amanatool.com, In-Stile and Rail System: ogee, #55436; bead, #55437; or concave, #55433; $155.