This universal rechargeable handle powers all Welch Allyn 3.5V instrument heads. It is well-balanced and rests comfortably in the hand. Its weight is evenly distributed end to end. It has an adjustable rheostat control; its free-floating reserve setting allows optimal intensity and battery life. The convenient built-in charger allows you to plug into any conventional wall outlet for overnight recharging. A long-lasting rechargeable nickel-cadmium battery is included. Its smooth, non-abrasive knurled finish ensures a no-slip grip. Its chrome-plated brass handles provide durable, long-life construction. It has a safety switch to prevent accidental draining of the battery. Metal head connectors for durability.