This recommended practice provides the design criteria for static elastomeric O-ring seals used specifically in engine and engine control systems. It provides axial compression (face type) groove dimensions for aerospace metric O-ring sizes specified in MA2010. The conditions considered to formulate the design criteria are also described, e.g., seal squeeze and groove volume to accommodate O-ring swell. NOTE: Tables of O-ring groove dimensions are included based on the design criteria specified herein. Dimensions in this document are in millimeters unless otherwise specified.