Hitches, like many things, often have slight variations in dimensions. The critical dimension for a hitch receiver is the I.D. or Interior Dimension (the space inside the hitch); the critical dimension for a hitch tongue is the O.D. or Outside Dimension.
Our engineers have designed the tongues of our hitch racks so they permit no play. However, some hitch receivers may have a slightly oversized I.D. thereby resulting in play or wobble.
Tightening the hitch bolt completely will reduce most side-to-side play. If you experience up and down play (or tightening doesn't eliminate side-to-side wobble), consider adding a shim -most hitch installers will have shims available or make one by cutting and folding an aluminium can.