This is a clamp for a speaker we are using in a robot design with an Arduino and Wave Shield. The design requirement which drove the fastener locations was the need to minimize the footprint. The speaker may safely overhang the side the bot we are designing.3 3mm washer (optional, we did not use) 3 3mm nut 3 3mm x 24mm nylon spacers (1" #4 spacers are fine) 3 3mm x 40mm bolt3.5"x7"x3mm (a.k.a. 0.125") acrylic, clearThe 40mm bolt was sized to go through another 3mm acrylic sheet, but it is tight. We decided to removed the washers and would have liked to have a few more mm, but our supplier only had 40 and 50mm.The speaker we were working with was a GF0771 or GF0771M. We are used the Mylar version. http://www.digikey.com/product-detail/en/GF0771M/GF0771M-ND/304454We built this assembly, but have not yet connected it to our wave shield or bot. Will update when we have.