GuerillaBeam allows you to build powerful modular and portable image projectors. Fits any 35mm lens and various flashlights and speedlights. Fits usual modern 5x5cm slides with 2mm (Agfa CS) or 2.5mm thickness. Robust 53x3mm threads will attach any 35mm lens and LED lights. Slots on the inside allow for embedding fresnel lenses (sized 48.5mm x 38.5mm x 0.5mm) or color gels. Use the topmost slot for boosting projection performance with a collecting lens. For more information or buying finished projectors please refer to http://gbeam.de (site is in English).I usually print it with 0.8mm wall thickness and ~23% fill density. 0.1mm layer thickness is recommended, but you can go up to 0.25mm if you're in a hurry. Support material is required for printing a correctly dimensioned slide slot. Without supports, you will get an ugly slide slot that's way too thin. See the attached screenshot for an illustration of proper supports. With Cura, supports will be automagically generated at just the right places by setting overhang angle for support to 51 degrees (Lines support type and 15% fill amount). With other slicers you should be able to find your own way.