They're great when they work .. !
You understand the cams on the two little screws to adjust the 'pinch' on the pinlock? Spread the visor out with hand and forearm on a tea towel on the kitchen work surface and adjust the cams so that they both point inwards ..
(As an aside ... I taught Mark Blundell to pass his bike test aver 25 years ago. Even then ... so 25 years ago .. he had a visor from one of his race lids that was one piece plastic but had a moulded air gap inside it. Why on earth can't they do that today on a motorcycle visor today .. ??)