The tights I have are just running tights. I use them just as a wicking layer under some lined running pants.
I will wear just the tights if the temp is in the 50's or so. I put the running pants on below about 50. That's all I wear down to about 10*F. Below 10 or so I throw some regular long underwear on over the running tights.
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Work: the 8 hours that separates bike rides.