Is there a significant difference between 3K and 4K pic quality on this site?

@ezromeo
Have a look here

https://www.istripper.com/fr/forum/thread/54753/1?post=779650

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For the girls that i've already downloaded at 3K, do I need to download them again at 4K?

If you have a 4K monitor or you play your cards at more than 100% it is probably worthwhile. Try an experiment, download one card you like at 4K and see if it's any better. 4k cards will require more storage space on you hard drive.