The most common of appliances are tankers, of which the most common of tankers are Category 1 Tankers, which is mainly used in a combination of rural and urban/interface roles ('interface' meaning where built-up areas meet bushland). The next most common fire appliances are Category 7 tankers which are used to support heavier appliances in fire fighting operations as well as being a primary appliance themselves. Category 9 appliances are most often used as rapid intervention vehicles (thus the name 'Striker') to attack small and spot fires quickly before they are able to spread.