1-647123-0 is a straight-post PCB header connector designed for 0.100-inch centerline spacing with retention pegs to secure the connector to printed circuit boards. The header features 0.025-inch square posts with a typical spacing of 0.100 inches between posts, and includes two retention pegs (one peg on 2-position headers) for mechanical stability. The overall length (dimension A) is calculated by multiplying 0.100 inches by the number of post positions, allowing for flexible configuration from 2 to 28 positions. Gold headers are duplex-plated with gold on the mating end of the post and tin on the solder tail, providing excellent electrical contact and solderability. This connector is commonly used in wire-to-board and board-to-board applications where reliable mechanical retention and consistent electrical performance are required.