This is the same cut down style guide that is standard with the Scaleauto Porsche 911 and BMW M3 cars. Prethreaded. Price is for two (2) guides.

Blade is 25mm long and undercut in the center area to reduce friction.  M50 x 2.5mm threading. Please note that this is not the same as the standard 3/16 threading common to American thread cutters and setups.