Micrometers comprising a measuring head, extension rods with or without spacing collars, handle (in smaller sizes). Three sizes of measuring head, in inch and metric units. Stick micrometers for measurement of greater internal lengths (6 in or 12 in micrometer unit, fitted with micrometer of 1 in range which, with series of extension rods, permits measurement up to maximum length required). Material, thimble and barrel, micrometer screw, extension rods, spacing collars, adjustment, accuracy, rigidity, handle, gap setting gauges, marking, case and packaging, test methods.Cross References:BS 84BS 817BS 818BS 852BS 863BS 869BS 870BS 887BS 888BS 906BS 907BS 939BS 957BS 958 BS 1054BS 1643BS 1685BS 1734BS 1790BS 2795