The RF 800mm F11 IS STM lens features an STM focusing system ideal for fast and quiet focusing when tracking elusive subjects out in nature. Additionally, an optical image stabilization system with up to 4 stops of shake correction makes it easy to use either hand-held or with a monopod. It will also accept an RF 1.4X or 2.0X teleconverter^ to increase your focal length to a staggering 1120mm or 1600mm respectively.
^ May lose AF functionality.
Read: Full Spec-Sheet (on Canon’s website)