This sale is for a near mint condition Mamiya RB67 Extension Tube 45mm (No.1). Sorry, no caps included.
There are minimal signs of use, just a few specks of lost paint on the locking ring; this tube has barely been used. It has been tested and works perfectly.
This extension tube will give you 0.35 to 0.72x magnification with a standard 127mm lens.
A copy of the instruction leaflet can be downloaded from the Downloads section of this website that gives full details of usage (essential for correct exposure if you do not have a metered finder).