Small bracket to hold a 12.5 mm diameter interference filter in front of a M12 (S-mount) lens. This is a small part with a fairly tight fit, so it required some work with an xacto knife and needle file to clean up, but after that it does fit well and hold the filter securely. OpenSCAD file provided to customize to other filters or lenses. It fits at least on this lens "PT-0818MP 8.0mm, F1.8 Mega Pixel" from www.m12lenses.com and this filter: "Optical Filter 850BP50 12.5 mm Bandpasss" from ebay.com/usr/bjomejag