The halves of a yo-yo are the two side sections that are joined together on each side of the axle and may be detached from or permanently secured to the axle. With halves that can be detached a yo-yo can be disassembled to remove knots or perform maintenance.
How the mass of the halves are distributed significantly affect a yo-yo's performance, appearance and feeling. Manufacturers and modders design and alter halves to enhance yo-yo performance and aesthetics.
- One way to alter halves is to add rim weight which increases spin time and resistance to unintentional precession(flopping over). Rim weighting does this by adding and changing the mass distribution which increases resistance to loss of momentum(slowing down) as well as increasing the moment of inertia(resisting precession). This can be done by putting metal or rubber rings under the side caps of both halves near the rims. Adding mass around the hubs has the opposite effect which eases looping and gyroscopic flops.