Features:
Suitable for M42 mount lens without focusing .
Can be used as a macro extension tube.
No electronic , manually controls aperture and focusing.
alloy material, machining, and sturdy.
Easy to install and simple to use.

Specifications:
Material: Alloy
Lens Compatibility: M42 screw mount lens
Length: 17mm-31mm/ 25mm-55mm/ 36mm-90mm(optional)

Packing List:
1 *