Mucking during primary and secondary extraction is done mainly with construction-type front-end loaders. Loader sizes vary from 4.2 to 4.6 m3 (5.5 to 6 yd3) with the preferred mode being the Caterpillar 980 series. These loaders provide fas cycling times and good operator comfort. Typically, these loaders are replaced or rebuilt after 15,000 hours when their maintenance requirements start to increase unacceptably.