confusion over DC power jack sizes (2.1mm, 2.0mm etc.)

[bdevlin]

I have a 1-spot and I need to buy mating female jacks for the daisy chain.  Am I looking for 2.1mm inside connection? And is it 6.5mm outside? 

[Derringer]

I have a 1-spot as well

these work perfectly
http://www.smallbearelec.com/Detail.bok?no=93

and there's also ones with external nuts if you prefer
http://www.smallbearelec.com/Detail.bok?no=666

[yeeshkul]

I get those standard plastic DC sockets with external nut from Smallbear. Those are 2.1mm, so if you use the same type get 2.1mm jack.