Fits 1 (one) PIR sensor in a 4x2x6 Brick. This mount is intended to hold up a PIR Sensor for prototyping some ideas. The brick itself is equal to 4 (2x6) Lego bricks. So it can be "bricked" into a nice support structure to hold it in place. A huge help when you are trying to make something and don't want your sensors out and loose. That can cause shorts, pulled wires, and or just slow you down. If you don't have a 3D printer but you're interested in getting one of these we can print you one at www.badbrick.com/catalog In MakerWare, I modify the "Medium" settings: Quality: Layer Height = 0.2 and I increase the temp to 240C to let the little larger prints fuse better. All other defaults are the same.