BDM 8760F 8 Ohm 15 watt Plastic Coned security Alarm Speaker measuring 3 1/2 inches square with mounting holes 2 13/16 inches across each other and 3 15/16 diagonaly. This speaker was used on a Brinks home security alarm  system. This speaker has been fully tested and is working perfectly. Please see pictures for detail. Thank you for looking.