Price: £9.17 GBP +VAT (£11.00)
Top quality Blau cap. If you have an unbranded cap which either came with an aftermarket header tank that you bought, or you sourced an unbranded cap elsewhere, DO NOT USE IT! See Header Tank Caps in the Cooling a Subaru Engine in a VW info page for more info. Use only genuine VW or Blau caps unless you don’t mind taking a massive, unnecessary risk.
Blau were the OEM to VW for the genuine VW branded caps. But they sell the version which has a different look with their own branding. This is apparently so they can sell their version to other, non VAG OEM’s (I believe some MAN trucks use it?). Presumably Blau designed the cap for VW, so own the IP.