THIS ITEM HAS BEEN DISCONTINUED-T12/F40 Fluorescent 4' DIMMING SLEEVE #4117-T12-Dimming4 These light stabilized unbreakable clear poly-carbonate U. V. filtering sleeves are designed to provide protection in case of fluorescent lamp failure. In addition to containing broken glass particles and lamp chemicals, which protect personnel from injury, the Fluorescent Dimming Sleeve allows you to regulate the light output or reduce lamp glare by simply turning the sleeve with your fingertips to your desired comfort level. End caps are included. F40-T12 lamps. Tubes measure: 46-1/4" long without end caps, 47-1/8" with end caps. 1-3/4" wide. 2 piece minimum.