Always used Mt500 Endura lycra shorts , had about 6 pairs over last 20 years. They still use shorts with that name but the ones available I have seen in shops are half the thickness and Chamois padding is the same pretty thin . I looked at the undershorts liner with same name but no mention of the padded arse bit. Shops I have tried have not been much help. I wonder how good the ones in pic are , the Chamois is not mentioned . Can't be bothered faffing about ordering stuff to send back . Thing is shops don't seem interested, I remember when I could go to a shop and order something now they don't offer that option.
The bib makes for one less article of clothing relying on a waistband to stay in place. Not cheap at c £70 but at least what you are paying for mostly is the chamois. Higher grades ( e.g 600) are even more expensive and like the bib liner have no armour.
