Power Drive Booster PB-E2 is an optional high-performance motor drive unit for the EOS-3. It boosts the camera's continuous shooting speed from 4.3 fps to as much as 7 fps (even in AI Servo AF), and makes vertical shooting easier with a comprehensive control layout including a shutter button, main dial, focusing point selector, and separate buttons for AE lock and FE lock. It is powered by 8 AA-size batteries (housed in included Battery Magazine BM-E2) or by Ni-MH Pack NP-E2 (optional), a rechargeable nickel metal-hydride pack. Power Drive Booster PB-E2 also has limited compatibility with the EOS-1 and EOS-1N.