These are .1 inch (2.54 mm) pitch headers; every workshop should have a good collection of these on hand. Stacking headers are useful for making daughterboards or shields for Arduino-like development boards. The extra long pins can extend through the PCB and allow for the stacking of shields. We purchase these headers in large quantities and make them available at a very decent price.
Also available in 1×8 and 1×10 options. For a standard Arduino shield you’ll need (1) 1×6, (2) 1×8, and (1) 1×10.