This 46mm Leica UVa filter is in very good condition with the exception of a 'DING' in the outer rim. Looks like the camera was laid down hard or maybe even dropped. It does not effect the threads connecting to the camera. Yes, if multiple filters were used during a single shoot on the same lens, this would need to be the outer-most' filter. No filters will screw on to the exterior of this filter. But if your'r loving fr a great piece of Leica 'glass' in a 46mm UV, it get's no better than this.