Synth relay grenade

The Synth relay grenade is a weapon in Fallout 4.

Characteristics
Toss a synth relay grenade to spawn synth reinforcements at a target location.

Locations
Obtained via a speech challenge during The Institute Quest: The Battle of Bunker Hill.

Allies of the Institute can also purchase synth relay grenades from the Institute requisitions vendor after all Main Quests are completed.

There is also 8 Synth Relay Grenades lying on a table, in the small weapons testing area of the Institute Advanced Systems area. Another 5 can be found on a shelf in the Institute SRB, along with some Institute pistols and fushion cells.