M42x1 (Universal / Pentax / Praktica)
The most widely used camera lens thread in history. Also called Pentax screw mount, Praktica thread, or Universal mount. Used on: Zenit SLRs (USSR/Russia), Praktica cameras (East Germany), Pentax Spotmatic, Fujica, Yashica, Ricoh, and hundreds of lens manufacturers worldwide. Still in use by KMZ (Cosina/Voigtländer). Also the standard thread for most enlarger lensboards and bellows extension tubes.











