Air-Flow TelsLightweight, ripstop nylon Air-Flow Tels attach to sails with waterproof adhesive locator discs. No holes required. Tels show the air flow across the sails – allowing you to trim sails for maximum performance. Each kit includes 14 Tels and full instructions on where to apply them and how to read them. Specifications:Instrument Function: WindBox Dimensions: 2″H x 4″W x 8″L WT: 0.05 lbsUPC: 011698009503Quick Guide (pdf)Brochure (pdf)