These are genuine GMK Screw-in Stabilizers, used to stabilize the longer keys on your keyboard.
Available in 6.25U, 7U, and 2U lengths, these stabilizers come with a screw-in mounting style for maximum reliability.
A Standard 60% board typically needs 4x 2u stabilizers and 1x 6.25u stabilizer. A Tsangan/HHKB/WKL 60% board needs 2x 2u stabilizer and 1x 7u stabilizer. A full sized board typically needs 7x 2u stabilizers and 1x 6.25 stabilizer.