PVC into Metal Drain...

hey folks, I took apart the bathroom sink PVC trap to get direct access to the metal drain pipe, so that I could auger the hell out of it to clear a clog. Once cleared, i reassembled everything back together but there seems to be an unexplainable clearance between the metal drain pipe and the pvc insert. I swear, there was no ferrule before or anything of that sort before I disassembled. What do I need to mate these two properly? What am I missing here?

Thanks,
Noob Sam

You need a slip joint washer

Thanks for the help, everyone. I was able to fix it. First of all, I bought a snake/spin tool and hooked it up to my drill and snaked the drain pipe thoroughly. Then, I bought a new nut and washer for the brass waste connector, and torqued it hard. No leaks out of that for another century… All is good, appreciate the help.