This is an expansion for the base game 5150.
From the publisher's website:
Infestation introduces the “tactical role-playing game” side of 5150. Players can use Infestation to “flesh out” their characters, giving them an almost life-like feel. Infestation blends the traditional RPG with fast and easy to follow combat on a personal level. Combining these two aspects allows players to enjoy the cinematic aspect of role-playing while keeping the excitement of a miniatures wargame.
Infestation covers...
Fast movement
Firing while fast moving
The H'DAN CORPORATION flash-bang grenade
New grenade throwing procedures
Explosions in confined spaces
Delayed explosions
New ranged combat chart
Specific hit locations and damage
Cover handled in a different way
Variable damage to figures
New melee system
Man Down check
Computers and hacking
New equipment
Encumbrance
Psionics with new QRS
"Half Deads"
Complete scenario that introduces new movement system
New "in encounter" encounter system
New variable time clock for encounters
Covert Operations Group with new QRS
Covert operations
Security robot - with new QRS HAFER-2 Security Bot
Xeogs are refreshed to use in the scenario if needed - with QRS
New way to play solitaire or same side two new aliens with QRS