https://www.canonrumors.com/here-are-the-rf-600mm-f-11-rf-800mm-f-11-super-telephoto-lenses/
Canon will announce some very interesting super-telephoto prime lenses on Thursday alongside the EOS R5 and EOS R6.
Canon RF 600mm f/11 IS STM Specifications:
Retractable design
10 elements in 7 groups
DO element
Minimum focusing distance 4.5m
Maximum magnification 0.14x
5 stops of IS
82mm filter size
Size: 93mm x 199.5mm (When retracted) 269.5mm when shooting
Weight: 930g
Canon RF800mm f/11 IS STM Specifications:
Retractable design
11 elements in 8 groups
DO element
Minimum focusing distance 6.0m
Maximum magnification 0.14x
4 stops of IS
95mm filter size
Size: 101.6mm x 281mm (When retracted) 351.8mm when shooting
Weight: 1260g