Our labor units are based on years of industry experience and feedback from our clients. We have various labor categories that we use. If you are a merit or union shop contractor, Candels will tailor the labor units/rates based on your economic and market situations. Candels also uses the NECA Manual of Labor Units for reference, especially for items that we seldom come across. It is well worth the money! To order one, click here. (Link: https://www.necanet.org/store/product/4090-19)