Sheffield Research is a division of General Technologies Corporation. Sheffield Research is a manufacturer of diagnostic tools and testing equipment for use in all types of automobiles. Fault finders, amp clamp multi-meters and various other circuit testers are some of their most popular products offered at DenLors. Sheffield has made a name for themselves by making circuit testing and pin pointing problems in electrical circuits easier with their line of specialty tools. See their products listed for sale below or visit their website at GTC.CA their phone number is 1-800-440-5582.