Currently Gio's studio use these anal tunnels to fill the asshole with pee like in this pic, being more or less often in wet scenes

To be honest, everything usefull to strech and promote the asshole play is welcome like big dildos(i miss the dildo intros that Gio used to shoot like the granade toy or that red buttplug, even the green snake), buttplugs or whatever.
davebowman, that kind of practice has been use in some american porn movies, definetly is super hot how looks the asshole wide open and streched by that plastic item and illuminated by a little light, perfect to fill the asshole with anything, even with a lot of spit