Hi Larry IPC-FC-250 "Performance Specification for Single and Double Sided Flexible Printed Wiring" would the equivalent performace specification. Though as the title states it does not cover multilayer. The document defines and specifies the performance testing and qualification requirements for each of the different product classes of single- and double-sided flexible circuits. Like all IPC specifications, inspection criteria and test methods are provided at the back of the document. Of additional benefit would be: IPC-MF-150F Metal Foil for Printed Wiring Applications IPC-FC-231C Flexible Bare Dielectric for Use in Flexible Printed Wiring IPC-FC-232C Adhesive Coated Films for Use as Cover Sheets for Flex Circuits IPC-FC-241C Flexible Metal Clad Dielectrics for Use in Fabrication of Flexible Printed Wiring IPC-RF-245A Performance Specification for Rigid Flex Printed Boards IPC-D-249 Design Standard for Flexible 1 and 2 Sided Printed Boards IPC-FA-251 Assembly Guidelines for Single and Double Sided Flexible Printed Circuits IPC-D-273 Design Guidelines for Multilayer Flexible Printed Wiring (I believe this is still in development) For the archive... MIL-STD-2118 Military Standard, Flexible and Rigid-Flex Printed Wiring for Electronic Equipment MIL-P-50884 Military Specification, Printed Wiring, Flexible and Rigid-Flex One caviat... Make your reference call outs based on real need. Take the time to review the specs before you call them out. Also there are some new materials entering the market that are not covered yet. These specs can provide some good boiler plate but your P.O. is the ultimate contolling document. Cheers! J. Fjelstad