NuVinci 27 tooth 410 sprocket (1/2" pitch and 1/8" wide teeth) is welded to the splined freewheel adaptor.
This does NOT fit the newer N360 hubs.
The washer is not included, so be sure and order it.
Use the 410 or 410H Chain (1/2" x 1/8") with this sprocket.
Your freewheel sprocket should be 1/2" x 3/32" wide so you can use your old pedal chain.
The Best Brand of freewheels to use with the set up is the DICTA brand due to the way they are made, thin design with the Four prongs inset.
Be sure and order the 1-3/8" ID x 2-1/8" OD, Zinc plated, Machined Washer.
http://www.staton-inc.com/store/products/NuVinci_1_375_ID_x_2_125_OD_Machined_Washer-527-20.html
The washer is used as a spacer to keep the two chains from touching with the NuVinci drive kits.
Using a 27 tooth sprocket on the older NuVinci Hub and a 26" wheel you should get the following speeds.
Your top speed will vary depending on many factors and may change by 5 +/- mph.
16 Tooth Freewheel should give you 29.59 mph - LOW 8.45 mph
17 Tooth Freewheel should give you 31.44 mph - LOW 8.98 mph
18 Tooth Freewheel should give you 33.29 mph - LOW 9.51 mph
20 Tooth Freewheel should give you 37.99 mph - LOW 10.85 mph
22 Tooth Freewheel should give you 40.68 mph - LOW 11.62 mph
To find all the types & sizes of adapters - adapter - adaptor - Track Cogs - Lock Rings - Track Cog & Three Prong Sprockets:
Type " FWADP " in the Search box.