In the UK I never fitted a air filter of any type, only A7SS, just a long bellmouth bought back in 1967, looked the business. But now living in Spain the dust is always about and the new 376 monobloc made by Burlen has already got wear marks on the slide. So the other day I bought and fitted the wire cone filter from Burlen, only just fits in the space between the battery carrier and the carb. Not sure if it will help keep the dust out but it looks okay.