I found this, what's the difference between a motor wheel drum and bud drum?

DORMAN Part # 610039 More Info {#6100391, 98147, 981471} Serrated Stud; Thread; 1/2-20; Knurl Dia.: .625"; Length: 1-5/8"; Shoulder Length: 23/32"
Front Right; 1-5/8" Length; w/10" Front Drum; Motor Wheel

$1.41
DORMAN Part # 610122 More Info {#2460614, 6101221} Serrated Stud; Thread; 1/2-20; Knurl Dia.: .650"; Length: 1-9/16"; Shoulder Length: 5/8"
Front Right; 1-9/16" Length; w/10" Front Drum; Budd