A bearing housing to receive and be deformed around a ball having a predetermined radius R to form a bearing, an inner surface of the bearing housing being generally cup-shaped, having at least approximately circular symmetry around a central axis, and comprising: a cup portion of the radius R shaped to seat closely a first portion of a ball of radius R placed in the bearing housing; and a conforming portion lying in the plane which is perpendicular to the central axis and contains the centre of curvature of the cup portion, there being a clearance between the conforming portion and a second portion of the ball, the clearance being greater than any clearance between the cup portion and the first portion of the ball, the bearing housing being shaped such that, when the bearing housing is deformed around a ball having radius R to form a bearing, the bearing housing is deformed so that the conforming portion matches closely the shape of the second portion of the ball.