This is a standard (size C) concave bearing that will fit any of our unresponsive yoyos. (Does not fit responsive or wooden yoyos, except Arrow.) The bearing has a concave surface on which the strings sits, rising up towards the edges. This ensures that the string sits in the middle of the bearing, not touching the sides of the yoyo or response system. Keeping the string away from the yoyo helps the yoyo spin longer, compared to a regular flat bearing. It also helps with complex string manoeuvres, where there are multiple layers of string around the bearing. Some bearings sit loosely on the bearing seat of the yoyo and can be removed by hand. Other yoyos have a very tight bearing seat and requite a multi-tool to remove the bearing. It is not recommended to remove bearings with pliers, because they can be bent or damaged.