Balances all side-draft, down-draft or up-draft carbs at both idle and running speeds. Fits all single, dual or 4-bbl. carbs. Universal adapter fits diam. from 1-9/16" to 2-7/8". Easy-to-read calibrated dial. Provides immediate indication that carburetors are "equal"no readjusting instrument needed. Large intake aperture prevents floating, assures exact synchronizing at lowest idling speeds and at increased RPMs. Does not slow speed of engine during tests.