Urth Manual Lens Mount Adapter for M42-Mount Lens to K-Mount Camera Body

Purchased for use on an older Pentax K100D to use as a body for old film lenses. Have tried 3 lenses; 55mm f/1.8, 135mm f/2.5 and 400mm f/5.6. All work fine and focus to infinity. The adapter sits flush to the camera mount when installed. Edges were slightly rough and will probably wear in with repeated installation and removal; the only reason this got 4 stars rather than 5. Only complaint is that the adapter is slightly difficult to remove, even when using the provided tool. It appears almost identical to the Pentax brand adapter I bought when I initially bought the camera. The 135mm lens does NOT accurately meter in Av mode (the other two are work perfectly) and so I have to use full-manual M mode and the AE-L button to set the exposure. Things must be set correctly in the Custom menu such as enabling the aperture ring and the Tv Shift in the AE-L button in order to use the M mode with a fully-manual lens.