I've only had to use one of these once and it held. That was a Maxalami one, pushed in with the pronged tool. The tyre was a 28mm on the rear, which I was inflating to 80psi at the time. That repair held the 80psi as well as the tyre had before the cut (a few psi loss in a week) and lasted 2,600km (on a tyre which had covered 2,900m prior to the 3-4mm glass cut near the centre of the tread. I retired the tyre due to wear, not due to the repair.