#10-32 UNF-2B thru means National fine series thread as said and the 10-32 is the diameter and thread count per inch. The Class 2B is the allowances and tolerances for obtaining the fit. This is a very detailed process of pitch diameter, major and minor diameter, root radius, etc... All in all summed up Class 2 specifications do vary from a fit with no play when the pitch diameters of mating parts are common to a fit with some play. Class 2 is the Cadillac of commercial screws. If you need more detailed information like how to inspect for class 2 please EMail me. ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################