The Mongoose Sabrosa frames have something called a "Slot Jocky-ITS" system which seems to be an EBB of some kind. They sold the Sabrosa as a 3 X 8, an SS, or with an 8 speed Alfine.

After researching and agonizing because they didn't have any mediums, I decided to go ahead and get a small figuring it might work better for a drop bar anyway. Unfortunately they sold out. Friday morning they had more, but I got an error about insufficient inventory before I could complete the order. After that they were listed as sold out again. Finally this morning I was able to order one.

I looked and looked at Mongoose's size specs for a similar model and measured my bikes which are already both a little on the small size for me. I figure if worse comes to worse I can turn it into a bike for my son when he gets a bit taller.

Very stoked about it though. I've been looking for a 700c aluminum frame with wide tire clearance and disc mounts. I won a $100 gift card at an LBS so that'll be good for one disc caliper and I have a few parts lying around.

Thanks to the OP for the heads up. Can't hardly go wrong on a $24.00 frame that totaled $42 including shipping.