The offer is for the cheaper generic plugs. not as comfortable for long periods of time/frequen use.
The company sensercom also do custom plugs for around £70, but you need to get the moulds done. you need to get this done by an audiologist or hearing aid fitting specialist. as I'm medically trained and working towards audiology career wise, was gonna look into training up in mould makin and then setting up mobile service to go round events/studios etc if there's interest. in the meantime can get referred via ya GP or try tappin the private health sector direct.
Penfold