The e*thirteen 30-tooth Guidering M narrow/wide chainring was hinted at earlier but lacked a few critical bits of info, namely the chainline offset since it’s not a flip-flop design like their larger single chainrings.
Where the 32-tooth count and up models are designed to mount with either side facing out and switch between a 49mm and 50mm chainline, the smaller 30t had to be offset from the spider enough for the chain to clear the arms. Thus, it gets a 47.5mm chainline, lining it up a bit better for the larger cogs.
Because of the different offset, they don’t recommend a chainguide. But, as with all single ring set ups these days, a clutch equipped rear derailleur is recommended. The ring’s bolt holes are threaded, so no need to back the bolts with nuts. Holes are sized for 104BCD cranksets. They say it’s good for 8/9/10/11 speed chains but state performance is best with 11 speed set ups.
Retail is $52.95 for this one, and their other sizes have dropped in price a bit to $43.95. They’re machined from their EXA+ alloy, are 5mm thick and weigh in at 36g. Available in black, red and blue, shipping now.