Wide angle eyepiece compatibility between brands

[CatfishKev]

Awhile back someone sold a vortex razor spotter with a swaro eyepiece. I remember asking if they had to do something special to make them work together and they said they just fit together.  Does anyone know if the kowa 660 series would take the swaro 20 / 50 wide angle eyepiece? I want to build a pair of Big eyes but kowa only has a 30 power wide angle eyepiece and I'd much rather have the 20 / 50x. 

[360 0r Better]

That would be a good question that Doug at camera land might be able to shed some light on