Yeah, I'm not all about size, but I am a big dude at 6'6". Not sure if buttholes scale up proportionately or not though lol. It definitely takes a decent bit to relax enough for it, getting past the outer sphincter is pretty quick but the internal sphincter is the one that takes a bit more time. Speaking of, iirc when boofing drugs you don't want to go past the internal sphincter since the rectal columns are best for absorbing