I have three RO sanders and this varible speed rigid is my favorite...Hands down.

my other two are a very old Makita, single speed and a dewalt single speed. The dewalt seems to vibrate a bit more than this Ridgid. With a shop vac hose used instead of the dust bag this thing collect nearly every bit of sawdust. The really long cord is nice too.

I unscrew the bag...and my shop vac hose fits perfectly in side the smaller center hole of the dust port. When the vac is "running" the suction holds it in place. I have two shop vacs...both Shop Vac brand ( I have a 5 and 8 gallon) the hose OD is about 1 to 1/4" )

If you have one of those monster sized hoses / vacs it might fit in the outer ring.