Tankers are used to transport crude oil and refined products in waterborne trade. Ship carrying crude oil or refined products. The tankers can be used in either “clean” (light refined products such as gasoline and diesel fuel) or “dirty” (residual fuel and crude oil) trade. The tankers range in size from the small vessels used to transport refined products to huge crude carriers. Tanker sizes are expressed in terms of deadweight tons (dwt). The smallest tankers are General Purpose which range from 10 to 25,000 tons and the largest are 550,000 tons. These tankers are used to transport refined products. Tankers are unloaded/loaded at the jetties or the specially build piers. If a ship is equipped to carry several types of cargo simultaneously the ship is called a Parcel Tanker. A Shuttle Tanker is a tanker carrying oil from offshore fields to terminals. An oil tanker especially built for the transportation of refined oil products, often with inside painted/coated tanks, is called a Product Tanker.