There is research / case studies showing that most people don't work a full 8 hours a day, that staying focused so long is next to impossible every single day, and that a shorter workday can increase productivity [0] [1]. With that in mind, what do you think of companies that offer such a work day? You could also do 5 hours a day for 4 days, but I think you'd gain more efficiency from an extra day rather than one extra hour a day, when after 4 hours can be tiring already.
[0] https://www.amazon.com/Five-Hour-Workday-Differently-Productivity-Happiness-ebook/dp/B01FGAFDBO
[1] https://www.amazon.com/Shorter-Work-Better-Smarter-Heres/dp/1541730712