The MC 2X teleconverter increases the focal length of any Kiev 60 lens you use it with by 2 times.
Using a 2X teleconverter with standard 80 mm lens makes the lens into a 160 mm lens which is perfect for portraits.
Even though there is a two-stop loss in effective aperture (as any 2X teleconverter), the 2X teleconverter maintains the closest focusing distance of the lens you use. Your lens aperture will still work automatically.
Optical block is separable. You can take it off and use convertor like regular macro tube.