HP 691740-005 is a 4-GB memory module for adding or replacing memory in a compatible computer. HP identifies this exact part number as a PC3L-12800 module rated at 1600 MHz.
The module is listed in HP’s service guide as a replaceable memory part. The guide covers it alongside a computer platform with SODIMM memory slots and DDR3L-1600 support, so this memory is intended for systems that support those specifications. Adding memory can provide more capacity for everyday computing and multitasking, within the limits of the host computer.
This part number identifies the 4-GB module; it is distinct from other capacities listed in the same guide.