CX used to have the stronest arrows on the market...they could stand an inpact on a steel bear and not blow up like most other brands...
However the nock would via Inertia, put hairline cracks in nock end of shaft...the Bulldog Collars prevented this from happening...
They also help on near hoods from damaging the nock end of the shaft...
I have the list of different sized collars but not with me at the time...but will look it up for you..
Neil