The Martin Handgrip Dynamometer uses a rubber bulb connected to a manometer to register grip strength. Values are read from the very clear analogue dial. This is fitted with a 'slave indicator' which automatically registers the highest reading, which is easily reset to zero. It is suitable for infants through to adults because of the 3 different sized bulbs that are supplied. Generally the large bulb would be used by adults and adolescents whose metacarpal circumference is greater than 19cm. The medium bulb is suitable for those with a metacarpal circumference of less than 19cm with the small bulb reserved for infants and those under 10 years. In addition, the strength of individual fingers can be tested using the small bulb.