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 901M Internal Micrometer has the following specification: Range: 25-55mm.Head Range: 5mm.Additional Information:Micrometer Type: InternalMetric/Imperial: MetricMin. Measurement (mm): 25Max. Measurement (mm): 55Graduation (mm): 0.01