This signal is handheld and initiated by a friction fuze that has no delay.
Its main tube consists of a firm but thin cardboard tube held in a thin metal tube base.
Bottom of the metal tube is threaded and held shut with an unpainted alumin ium cap.
Under this cap the pull cord and ring are situated.
See this small internet film on the use of the ROS serie.
Length : 206mm
Diameter : 41mm
Photos thanks to Jarda.