157mm I.D on mask.
Nikkor 400mm

Bahtinov Focus Mask for Nikkor 400mm Lens. If your camera has long lense , enough pixals and you enjoy the night sky, this is for you.
Place it on the lense
Point towards a bright object
Manually focus for the center line to be right between the angled ones.
Fast usps shipping.  Made from spencer 3d. Color black but other colors available just ask. Fast USPS 2-4 Day SHIPPING. Also fits any 157mm outer diameter telescope or Camera Lens.

SHIPPING CHARGES ARE SLOWLY CHANGING! MOST ITEMS THAT WAS FREE SHIP WILL BE CHANGING OVER TO CHARGED SHIPPING TO THE BUYER, DUE TO INCREASE CHAEGES OF SHIPPING AND SHIPPING SUPPLIES. BUT THIS WILL ALSO MEAN LOWER PRICES ON THE ITEMS, AND MORE SHIPPING OPTIONS, AS WELL AS FASTER SHIPPING OPTIONS. THIS ALSO MEANS MORE ITEMS AVAILABLE FOR INTERNATIONAL SELLS.