I have the Swarovski doubler for my 10x42's. Seemed like a good idea since I use my 42's off the tripod a lot, however, it is useless. FOV is terrible and image quality is compromised and low light is terrible. I find the doubler more useful as quick reference glass from the pocket then as an attachment to my eyepiece. I would definately recommend you do not spend the money. In my case, the swaro attachment just to mount on the binos on the tripod was a hundred bucks+, throw in the actual cost of the doubler and you are paying a fair amount for a marginal system. Swarovski makes great stuff, and I love my binos, but the double system just doesn't work.