Tamron-F SP Tele-Converter 2X KR BBAR MC7 for Pentax K center This is a high quality

This is a high quality macro bellows system for M42 thread mount cameras and lenses

But everyting else is solid

without diaphragm or focusing helicoid

which is very helpful context

Tamron-F SP Tele-Converter 2X KR BBAR MC7 for Pentax K center This is a high qualityThe Tamron F SP Tele Converter 2X KR BBAR MC7 is a good quality manual focus teleconverter for Pentax K mount lenses. It's got electronic passthrough for A type lenses, but no autofocus capability. In very good condition, with light cosmetic finish wear; clean glass, good function. A teleconverter will double the focal length of your lens, at the cost of a few stops of light.