This one starts out as a 22 or 24t ..
http://www.sram.com/truvativ/product...dt-am-crankset
and has a cable shifted planetary 1.6X overdrive
this one has a 28t ..
http://metropoliscomponents.com/patterson.htm same 1.6X so a 44.8't'
I Have a double planetary shift of a Schlumpf Mountain Drive, and a S-A AW3.
Simultaneous double shifts work well with just a moments pause in pedaling .
by the way substituting a Sachs indicator chain gripper, on a Sturmey hub,
http://www.sjscycles.co.uk/brompton-...ram-prod13630/
you leave the nut on the indicator chain, and the gripper is using a spring ..
essentially a QR. rather than unscrewing the barrel adjuster,
when you mend a puncture it's one less thing to fuss with..