Kill the nest! Combat® Max™ Roach Killing Gel formula attracts roaches with the food and water they need. This roach-killing gel starts killing both large and small roaches within a matter of hours. Apply this gel behind appliances and in cracks and crevices where roaches make their nests or enter your home. Because Combat® Max™ Roach Killing Gel allows you to place baits throughout your home, more roaches can find and eat the bait, resulting in a quicker and more thorough kill.