The MUAC measure is a long strip with a series of colour bands. When measured properly against a bare upper arm, the gauge provides a number and indicates the colour range

From the MSF Refugee Handbook

Screening for malnutrition

"It is essential to detect children with nutritional problems early on as malnutrition is a major cause of mortality among children. For screening purposes, it is recommended to use the mid-upper arm circumference measure (MUAC), which is a quick way of identifying children at risk. Referral to feeding programmes must be organised in line with MUAC cut-off points and the criteria selected. The time and resources devoted to malnutrition will depend on the degree to which malnutrition is a cause of mortality."