The silver bit slides and presses on the valve when you press it. You can also put valve caps on them or even more extensions a la ^^
edit: missed your earlier post. Tufo make extensions where you remove the valve workings, put on the extension then replace the workings. If I lived in london I would show you my spares
I use Topeak

The silver bit slides and presses on the valve when you press it. You can also put valve caps on them or even more extensions a la ^^
edit: missed your earlier post. Tufo make extensions where you remove the valve workings, put on the extension then replace the workings. If I lived in london I would show you my spares