Protherm Engineering Pvt. Ltd. Supplies Polyester Round Slings. Protherm Engineering Pvt. Ltd. Offers a range of Slings that includes Polyester endless Round slings, Polyester webbing slings, Ratchet lashing system and multi-leg sling in Chain, Wire Rope & Webbing slings. The Polyester Round Slings are available up to 200 tons double path slings. The Polyester Round slings are made by the Polyester Yarn Hank wound Continuously together in the form of the Endless Sling in the protective cover sleeve. These slings are available up to 200 Tons lifting capacity and slings are also color coded.