Surface-mount speaker is a premium full-range 3 inch, with overall dimensions smaller than a 4 inch sphere. It incorporates a proprietary attachment with indexed swivel-joint for complete hemispherical aiming. Components have been weatherized for indoor/outdoor applications. The SM31-EZ is an 8 ohm speaker without transformer. It is shipped with the AC-SM31-XFMR transformer module to add a 20W transformer and 5 position tap switch that mounts into a single-gang deep junction box.