Guess I should have asked before I bought the eye cover on Ebay 
but I have a Vortex Viper PST 4-16x50, which Butler Creek flip up cover size works for the front? I bought a 10 and it’s too small. I have a 16 from another scope and it’s a little too big.
I am using a 16 eye and a 43 objective and they both fit nice and snug on the same scope.