Through proven performance, patented VT/VTF Series have earned worldwide acclaim for service reliability.These cost-effective units offer compact size, functional flexibility, optimum intelligibility, effective sound distribution, and high-level output.All models contain a highefficiency compression driver with maximum acoustic conversion efficiency.(A quality which reduces number of units needed to attain specified sound pressure levels and provides substantial savings in amplification-power requirements and labor costs.) Die-cast, water-sealed construction withstands vandalism, vermin, moisture, corrosion, and vibration during indoor or outdoor use.Selection includes a basic 8-ohm version and 70.7 or 25-volt transformer models with DC blocking capacitor (C) where noted.All models terminate via barrier strips.VT Series models are surface-mount units; VTF Series are flush-mount units for recessed installation.VT Series mounts standard 4" E.O. Boxes; VTF Series mount 4" or 411/16" SQ backboxes and require model AR or MR adapter rings respectively (order separately) Optional mounting accessories are offered including: indoor and outdoor enclosures, a bi-directional housing, adapter plates and rings. Suffix model with color: Red (R) or Neutral Gray (N). Ex: VT-157UCS.