This paper describes a set of metrics and supporting benchmarking protocols for determining the performance characteristics of robot end-effectors. In the short-term, these tools are proving useful as a common ground for assessing and comparing end-effectors. The long-term goal is a standard framework for providing technical specifications for robotic end-effectors to help pair technologies to application spaces. This paper presents a subset of the metrics - grasp strength, grasp cycle time, finger strength, and finger repeatability - with accompanying measurement techniques and supporting test artifacts. The application of these metrics and protocols is demonstrated using example implementations to characterize a variety of robot end-effectors, with example data sets and test designs provided for downloading.