Lightweight, 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. Product : DAVIS AIR-FLOW TELS SET OF 14 Manufacturer : DAVIS INSTRUMENTS Manufacturer Part No : 950 UPC : 011698009503