"Legal for trade" scales are approved weighing machines to be used primarily in businesses that sell products by weight. Of course, it is a good idea to use legal for trade weighing and measuring machines for commercial as well as non-commercial activities. Using approved weighing and measuring equipment ensures uniformity so a certain product weighs the same everywhere and on any type of weighing machine. This helps avoid price related ambiguity. The National Type Evaluation Program (NTEP) managed by the National Conference on Weights and Measures (NCWM) is responsible for defining legal for trade scales. It evaluates and certifies all new weighing products to be introduced in the market. Many States require NTEP certification prior to installation of a measuring device. The fact that a weighing machine is legal for trade indicates that it has passed certain quality tests and adheres to protocols designed specifically for measuring objects. Before certifying a balance as legal for trade, it is tested for accuracy more than 100,000 times with a load of half its capacity. Other tests carried out are effects of temperature and a specific voltage range.