This filter is much better than the cheap 3rd party ones. Does not impact image quality and provides great protection to my 12-40 f2.8 lens.

After purchasing the EM-1 and several PRO lenses, I wanted to protect my new M.Zuiko ED 12-40mm f2.8 PRO, but this filter was not available at the time. So when it did become available, I made the purchase, and feel more comfortable that my lense has some protection ... after all, a filter is much cheaper to replace, and allows me to benefit from the weatherproof options of my body and lense without worry about potential damage to the lense.