This is a Bahtinov Mask that will fit the ZWO SeeStar astrophotography device. It allows for checking and fine tuning of focus against a bright star. If you are new to focusing with a Bahtinov Mask, please watch a youtube video on the subject.
Note: There are two profiles in this print. One has the Bahtinov Mask using tabs for the friction fit, the other is a full circle of material being used for the friction fit.