I have used the Ruby Beholder (still have it but rarely use it now) but not the glasses, I'm sure they do the same thing by allowing the values of the fabrics to show rather than the colours. When I first started quilting in the early 90's they were very popular but now I never see anyone at retreats using them. I remember at that time people mentioned to go to an office store and buy a sheet of red plastic page protectors and they would work as well. I didn't look to see the price of the glasses, but maybe that would be another option for you?