A bearing comprises an inner wheel, an outer wheel which includes a first outer wheel and a second outer wheel, a plurality of rolling elements which are disposed between the inner wheel and the outer wheel, an inner wheel elastic ring which is disposed between the inner wheel and the a plurality of rolling elements and an outer wheel elastic ring which is disposed between the outer wheel and the a plurality of rolling elements. The bearing also comprises a first boss part which is disposed on an outer portion of the first outer wheel and has a plurality of fixing holes, and a second boss part which is disposed on an outer edge portion of the second wheel and has a plurality of hook parts, where the plurality of hook parts are inserted into the plurality of fixing holes.