Those blades fit the older Keetons as well, not just the Hendrixson head.
If I didn't already have a lifetime supply of them, bought from Bob's widow, I would get a couple boxes.
The blades in the two boxes are identical. The Red package was the original release and Bob wanted to upgrade the packaging and call them Premium.
The number of blades per pack and the color of the box are the only differences.
I just checked one against a C&H blade and they are the same size from the edge to the back, and about 1/8" shorter end to end.
They do fit my 60" Barton Manual cutter.