This is a training grenade similar in shape to the No. 36M Mk I grenade.  It is designed to simulate the action of a bursting grenade.  Introduced on 6 July 1942.

The body is basically oval in shape with some having sixteen longitudinal grooves on the straight sides of the body to provide a firm gripping surface.  The body, made of clay, is drilled from the top to within ½ inch of the bottom.  The bursting charge consists of a rolled paper sleeve filled with 11.5 grams of G12 gunpowder.  The ends of the tube are closed by cork discs.  The charge is ignited by a 2 inch length of No. 11 Mk. 2 safety fuze that passes through the cork disc into the main charge.  A steel or copper ferrule is crimped onto the exposed end of the fuze with the open end filled with match head composition.  The burster is waxed and the exterior of the fuze shellac varnished for waterproofing.  Once the burster is inserted into the grenade body the open top is filled with bitumen.

The body is painted white with a ¼ inch red filling ring around the top.

For use, the match head is struck with a brassard and the grenade immediately thrown.  The match head ignites the fuze that burns for 5 seconds.  After the delay the fuze flashes from the bottom end into the gunpowder which then ignites.  The grenade gives a sharp bang and puff of smoke.  A reasonable safety distance must be maintained due to the danger of lumps of clay being projected.