These 40-pin 2x20 male headers can be used on a Pi Zero or a pHAT to break out the pins.
You can choose either straight or at a 90° angle.
Add one to a Pi Zero for compatibility with HATs (which use a female header).
Can be used to solder a Pi Zero and pHAT permanently together.
The 90° version is great for mounting inside projects at a right-angle or for routing wiring back underneath a HAT where space is at a premium but you don't want to solder wires directly onto your precious boards.