tThe Gen 1 Razors were the same focal length as the Swaro 65's and 80's. Also used the same bayonet mount as swaro. Hence the interchangeability... The new vortex's don't swap. I think that the Burris eyepieces will also swap, but don't know the focal length to determine accuracy.
The bayonet system on the eyepiece does make it more difficult in changing over to a different eyepiece other than those offered by the scope maker.
Back when the old 1" threaded eyepieces were common there were lots of options for eyepiece swaps.
Focal length issues can be overcome by seating the eyepiece to the proper depth in the scope. Moving the objective lens in or out will accomplish that also.
You can remove the eyepiece from the scope, then just hold a smaller diameter one into the scope in order to see this.
If the scope has a threaded area for installing an eyepiece cap, those threads can also be used for installing different eyepieces without the bayonet connection.
It requires an attachment with 2 sets of threads.
One for attaching it to the scope via the scope cap thread, the other for attaching a threaded eyepiece.
The eyepiece needs to be threaded into the scope till the focal length is correct.
Then locked in place with a small set screw, or possibly locktite.
I have a large set of 15 power eyepieces in my older pair of Kowa 77 mm TSN2s in a bracket by using this method.
The eyepieces are very good quality and intended for use in astronomical telescopes. They needed to be threaded in order to be used for my purpose.
I also have a set of adapters made for attaching to the same threads.
With those i can use any standard 1" threaded eyepiece of any power.
