K&F Concept PK-E and bonus M42-NEX metal lens mounts Thank you for viewing. The K&F PK-E is a mount adapter that came as a bonus when I previously purchased a used SONY α7Ⅲ. I used it to attach Pentax K-mount lenses to my A7M3. The bonus Dollies M42-NEX was purchased new on Amazon. I haven't had a chance to use it, so it's unused. While the Amazon reviews are good, I haven't confirmed its operation, and it's from an unknown manufacturer, so I'm including it as a bonus.