Because of the limited nature of the No. 6 concussion grenade as an anti-infantry measure during World War 1 (1914-1918), the No. 7 fragmentation grenade was developed. Both appeared - along with several other interim grenade solutions - during 1915. And like many of these temporary models, the No. 7 held a short service life as a frontline weapon. The British undertook these programs to help shore up limitations in their earlier No. 1 hand grenade series.
The No. 7 relied on a dual casing design approach featuring an inner and outer layer. The inner section held the explosive filling while the other section was filled with metal scraps which were thrown about when the grenade detonated. The No. 7 was heavier than the original No. 6 line and thusly the latter was favored by British infantry. A timed friction-based fuse arrangement was used for detonating both grenades. Despite entry in 1915, both the No. 6 and No. 7 grenades were already declared obsolete by the end of 1915. Regardless, existing stocks soldiered on to about 1917 as any and all weapons were needed for the war effort.