Ideally suited for mounting printed circuit boards horizontally. Internal sides of enclosure are smooth for easy connector installation except for the largest enclosure. 1591XXF. 1591XXF size is a universal type which includes P.C.board standoffs in the lid and enclosure PLUS includes card guides. Strong tongue and groove lid to box construction provides protection against access of dust and splashing water. Designed to meet IP54. Lid and box both contain - molded in PC board standoffs. Standard black and gray versions molded from easy to machine, flame retardant ABS plastic (material carries a UL flammability rating of 94V-0). Transparent blue and all economy versions are molded from general purpose (not flameretardant) plastic. Stocked in satin texture black and grey. On standard versions, the lid is secured with M3 x 10 mm Phillips machine screws threaded into integral brass bushings. Perfect for applications with repetitive assembly and disassembly are required. Economy versions are assembled with self tapping screws into fully plastic posts. Black and transparent blue enclosures include black screws, gray enclosures include nickel plated screws