A hairspring collet for press-fitting onto a staff of a balance wheel for a timepiece and providing interference engagement and an interference fit with the cylindrical outer surface of the staff the staff having cylindrical outer surface which is at a radial distance from the central axis of the staff, said hairspring collet comprising: a plurality of circumferentially extending elastically deformable interconnected arm portions, the arm portions forming an annulus having a central axis and providing an aperture therebetween, wherein each arm portion includes a curved concave engagement portion for providing a contact surface having an arc length for contact and engagement with the cylindrical outer surface of a staff of a balance wheel, said engagement portions being equally radially spaced from said central axis of the annulus at a first distance, and said engagement portions have a radius of curvature such that upon press-fitting the hairspring collet to the staff the arm portions deform and the contact surfaces of the engagement portions engage with and substantially conform with the outer surface of said staff along their arc lengths and interference engagement and an interference fit is formed therebetween; wherein stress induced from press-fitting the hairspring collet onto the staff is transferred and distributed from along the engagement portions to the arm portions adjacent the engagement portions and distributed therein; and wherein the press-fitting of the engagement portions with the staff substantially prevents relative movement between the hairspring collet and the staff of the balance wheel upon application of load from a hairspring in use in a timepiece movement; and wherein the hairspring collet is formed from a brittle material including silicon and quartz. a plurality of circumferentially extending elastically deformable interconnected arm portions, the arm portions forming an annulus having a central axis and providing an aperture therebetween, wherein each arm portion includes a curved concave engagement portion for providing a contact surface having an arc length for contact and engagement with the cylindrical outer surface of a staff of a balance wheel, said engagement portions being equally radially spaced from said central axis of the annulus at a first distance, and said engagement portions have a radius of curvature such that upon press-fitting the hairspring collet to the staff the arm portions deform and the contact surfaces of the engagement portions engage with and substantially conform with the outer surface of said staff along their arc lengths and interference engagement and an interference fit is formed therebetween; wherein stress induced from press-fitting the hairspring collet onto the staff is transferred and distributed from along the engagement portions to the arm portions adjacent the engagement portions and distributed therein; and wherein the press-fitting of the engagement portions with the staff substantially prevents relative movement between the hairspring collet and the staff of the balance wheel upon application of load from a hairspring in use in a timepiece movement; and wherein the hairspring collet is formed from a brittle material including silicon and quartz.