[ Flex Theme ] How can I change the size of Collection banner for different collections

[Emmanuel_Guzman]

Hello guys I am using the flex theme and so far I love it, The only thing that I need to change for further optimization is to change the Collection banner height to smaller size but I can’t so far because the flex theme expands any sized banner I upload to 1800 x 800px automatically. Which is fine for the banner image that works for one collection but Ideally for the rest of the collections I would prefer for the banner size to be 1800 x 300px format. I don’t have an option to change the size in the theme editor, how can I go about fixing this with CSS? any help would be much appreciated as I intend to make this change a soon as possible.