This fragmentation rifle grenade was an improvement of the No.20.
The detonator had to be loaded by the user.
There are several different HE fillings used on this type.

Length body with fuze: 137mm.
Length body w/o fuze: 101mm.
Length rod: 381mm.
Diameter: 35mm.
Weight: 510gram including 42gram charge.

Photos © Dave.

Mk1 :

Mk2 :