Experience with Binocular "Doubler" eyepiece?

[Mer19]

I was wondering if anyone has experience using a binocular doubler eyepiece and whether or not it's worth the investment?
I have 10X42 Meostars.
Thanks for any input.

 

[gr8fuldoug]

STAY AWAY from binocular doublers. They cut both light transmission and optical quality

 

[Lwilliams]

Nailed it on the head.