An object of the present invention is to provide a golf ball which is excellent in abrasion-resistance and durability. When a unicast data packet is received at a first of said units and the unicast data packet has a destination address which is not the subject of an entry in the forwarding database of the first unit, the unicast data packet is sent by way of the cascade to the other units in the stack, accompanied by a flag. Meter data can be read, and the meter can be controlled via communication with a wireless network using, e. In another aspect, a helmet mount for an optical device comprises a track assembly attached to a helmet to allow stowing of the optical device in a further retracted position.