It is a bias velve from a Fiat Uno and made adjustable by bolting it into a 'box' of 3mm steel with a threaded section to accept a bolt and lock nut. Totally un needed if using disc up front and drums at the rear. Mine is permanently off and was the only thing that was dubious at SVA, the tester said it was adjustable, I said it wasn't - he had to agree when I told him to adjust it. The bolt was in my pocket!!
