The Moore & Wright 900 Series Internal Micrometers comprise of a measuring head, a set of extension rods and a spacing collar to facilitate alternative measuring ranges. These models (901, 902 & 903) have detachable extension handles. All models supplied in a fitted case. These 900 Series Internal Micrometers conform to BS959 Standards. The Moore & Wright Internal Micrometer 903 Internal Micrometer has the following specification: Range: 2-12in. Head Range: 0.50in.