Let me introduce you to an excellent vintage lens, production of the USSR.
 
MC K1 2x Tele Converter for Zenit, Pentax, Praktica. M42 screw mount.

Teleconverter MC K-1 M42 is designed to increase the focal length of the lens by 2 times. Suitable for any cameras with M42 mount, such as Zenit, Pentax, Praktica, etc. It was available in the M42 lens mount. 

Through appropriate adapter this lens can be installed on any modern SLR and mirrorless cameras, such as Canan EOS, Nikon, Pentax, Sony and more. (Adapter not included).

Included is the front cap, original case.

Item specification:
Lens mount: M42
Focal length multiplier: 2x
       
Condition:
As you can see in the photos - it's in Very Good Working Condition. Front and rear lenses are clean. Inside there are a couple of dust.

Payment:
Payment should be sent within 3 days after purchase. Otherwise I can't guarantee availability of the item. 
I'm not responsible for any customs tax that can be charged in a country of delivery. Please, get known the customs rules in your country before bidding.

Shipping Policy:
Shipping from Ukraine. Shipping available Worldwide. I'll ship via registered airmail during 1-3 working days after payment is received. Item are carefully packed usually with bubble wrap in carton boxes.

Don't worry, delivery from Ukraine works as usual! All parcels are shipped from Kyiv on time, however, delivery times depend on transport companies that transit outside of Ukraine. In any case, all parcels are delivered. There may be delays, but this has nothing to do with events in my country!

Save on shipping! When buying multiple items, shipping is combined! I recalculate the shipping cost and issue an invoice for payment, taking into account the total weight of the package.

Return Policy:
Item must be returned within 14 days after the buyer receives the item. Shipping fee will not be refunded. All items must be return in original conditions without any physical changes with all of its components.
Return shipping charges are the sole responsibility of the customer.

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If you have any questions - Please ask! I will try to answer in detail!

Please see my other offers! There are many interesting items!