looks like the same type of vertical slits that LianLi used in the o11, they make an insane noise when air pass through I dremeled all mine top-left-rear-bottom and only left the dust filters where needed, I only regret cutting the top one because of LianLi design 😛 the grill isn't even in front of the fans itr's larger so I see an ugly part now yes the holes matter : +4.5dB because of the "angled slats" design https://www.pugetsystems.com/labs/articles/Effects-of-Grill-Patterns-on-Fan-Performance-Noise-107/ I googled after my own tests to see if I was crazy, tested in those configurations : air-old school wire grill-the hexagonal holes case thing-radiator and against the lian li case slats but nope sure is the worst design sound level wise noctua-corsair-bequiet all made a noticeably more annoying noise in front of those