Orientability is an important performance index to evaluate the dexterity of haptic master devices. Currently, most of the existing haptic master devices have limited workspace and limited dexterity. In this paper, we present the RemoT-ARM, a 6 Degree-of-Freedom (DOF) haptic master device that can provide larger and more dexterous workspace for operators. To evaluate its reachability of orientations, we propose a novel orientability index. Furthermore, a relative orientability index is proposed to characterize the matching degree of the workspace of a given manipulator to its target workspace. The volume, the manipulability and the condition number are also introduced as performance indices to evaluate the size and the isotropy of the workspace. According to these performance indices, all possible configurations for the RemoT-ARM have been taken into consideration, analyzed, and compared to finalize its optimal configuration.