some do, some dont. id say probably most do though. but if not, you could, you could fill up any old bong with ice. ice essentially just sits in there and when smoke passes by it, it cools it down making your hit smoother and denser. although the bong might get quite cold. normal ice notches keep the cold from the bottom of the bong so it doesnt get freezing
but what im asking is, if i just put ice over the percs, will it block them or something, or is that ok?
i seriously doubt it will block them. i used to have an ice catcher bong with a perc right undr it. the bong was big and the ice usually just feel through after a hit or two. it never blocked the holes on the perc
i use to put ice in my mad scientist right on top of the perc and after awhile the hole where u hook on top of the perc cracked so i had to buy another 1 and i stop putting ice on top of the perc so i start using ice water