The Diamond 580 is virtually unique amongst fountain pens in that it can be completely disassembled by the user for cleaning and servicing and experienced users are encouraged to do so. Full servicing instructions are included with the pen as well as a small wrench to remove the piston mechanism and a bottle of silicone lubricant for the piston mechanism (download manual here).
Nib length = 18.2mm
Section length = 21mm
Section diameter (max/min) = 10.0/9.3mm
Barrel diameter (max) = 13.1mm
Total length (not posted, including nib) = 129mm
Total length posted (including nib) = 175mm
Weight = 29g