Hi! I currently have this diffuser: http://www.grasscity.com/online_headshop/ehle-expanding-diffuser---145-to-188-flame-polish-logo.cfm I'm thinking about buying this ash-catcher: http://www.grasscity.com/online_headshop/ehle-ash-catcher---dry-system.cfm?iProductID=5889 Which size will fit my piece 14,5mm or 18,8?