Cooling Sleeves is a technology that can be researched at the War Center in Tech Level 3. It costs 250 Food and 150 Nova, and gives +1 attack to all Mech Factory and Troop Center units, except the Anti-Air Trooper. Primary Focusing Coils must be researched before it becomes available, and Cooling Sleeves is a requirement for Advanced Power Pack.
The extra attack is a tiny improvement, but can be decisive in battle, and the technology affects a great number of units.
"At Tech Level 3, further enhancements to your Troopers' and Mechs' blasters can make their firepower even stronger."
—Manual description