In the field of 5 to 100 kg load transportation in workshops, many systems having more or less complex ar-chitectures have been developed to reduce musculo-skeletal disorders (hoists, pliers, dedicated systems). These systems offer different behaviors and human interaction is far from being the same for all of them. In recent years, the literature produced a lot of work around design thinking, user-centered approaches emphasizing notions around perception, cognition, and ergonomics to meet the needs of the end user. The development of cobotics and more generally systems allowing the interaction or co-manipulation of objects highlights the notion of transparency of the system. This transparency is expressed as the fact of feeling only a part of the physical magnitudes of the object most relevant to the user in his manipulation. In the context of this article, we study the transparency of a kinematically redundant passive mechanism based on a scara one (revolute joints parallel between them) when manipulating heavy objects on a plane. This article is based on a state of the art of different criteria in order to evaluate the behavior of a robot such as manipulability or dexterity. We will indicate the relevance of these criteria that we apply to a theoretical study. These theoretical aspects will then be evaluated on Neoditech Scara Parts arm. It is a mechanism capable of handling up to 50kg composed of a plane arm mounted on vertical linear axis itself mounted on a fixed or mobile base. This plane arm consists of 6 revolute joints having parallel axes ensuring redundancy in the architecture of the robot.