User blog comment:Rappy 4187/Technical Update: June 28, 2017/@comment-1757994-20170628203455/@comment-1757994-20170629022847

Oops. I was thinking of AT&T 6rd when I said some ISPs hand out /48s. AT&T 6rd hands out /60s, which would be a range of 2^68 addresses. I suppose there could still be ISPs that hand out /48s, but the AT&T blocks are the largest I know.