Development

Ship-borne plane
(Higher chance if flagship is an aircraft carrier)

Commander level guideline is 20. For particularly rare equipment more than 30.

Machine gun, cannon, shell
(Higher chance if flagship is a battleship)

Commander level guideline is 20. For particularly rare equipment more than 30.

Sonar and depth charges
(Higher chance if flagship is a light cruiser or destroyer)

Commander level guideline is 10. For particularly rare equipment more than 20.

Radar
Radar improves accuracy, anti-air, and contributes to fleet-wide air superiority.

Commander level guideline is 20. For particularly rare equipment more than 30.

Engine
Engines increase evasion.

(Higher chance if flagship is an aircraft carrier or battleship)

Commander level guideline is 20.