If you’re looking to work for Google, Microsoft, or Facebook – be prepared for a fairly grueling interview process.

That’s the takeaway from a new study from Glassdoor. The workplace tracking company looked at average interview ratings of some top companies (a metric that Glassdoor already measures) and found that among the major tech companies, it’s hardest to interview at Google.

Google actually finished 8th on the list of the 25 hardest interviews with a difficulty score of 3.6 out of 5. 62% of former interviewees gave the experience a positive rating, however, with only 21% giving it a negative rating. The average length of the entire interview process at Google is 37 days.

Moving on down the list, Microsoft placed 16th with a difficulty rating of 3.4. The average length of the process there was 29 days.

Facebook apparently has a less strenuous process – but hard enough to land it on Glassdoor’s top 25 list. Coming in #22, Facebook’s interview process lasts 30 days on average and was given an average difficulty of 3.3.

Consulting firm McKinney & Company topped the list.

Bottom line – the interviewing process at some of these companies is pretty brutal.

But once you get there, you’re likely to approve of the management – at least the top dogs. Earlier this year, Glassdoor conducted another sort of study – this one into the confidence ratings of various CEOs. In other words, Glassdoor looked at how many employees approve of the job their fearless leaders (CEOs) are doing. Facebook’s Mark Zuckerberg topped the list with a 99% approval rating.

Other notable CEOs from tech made the list, including Google’s Larry Page, who came in 11th with a 95% approval rating. Amazon’s Jeff Bezos took 16th with a 93% rating and Dell’s Michael Dell came in 49th with an 81% rating. Back in 2012, Apple’s Tim Cook took the crown. This year, he has slipped to #18 on the list.