Robotic exoskeleton arms have been around for a long time and they have successfully evolved from research prototypes to commercial products. Multipurpose supernumerary robotic limbs (MSRLs) have been recently introduced as new types of aids which do not directly replace missing limbs, but they are additional mechanical arms with changeable end-effectors which can be worn by the user to provide needed functionalities. This paper presents the mechanical design and kinematics modelling and control of a MSRL system. The MSRL presented could have good application in industrial and domestic situations.