Relation of matched discs to matched circles for the Poincaré dodecahedral space, with injectivity radius r_inj = (π/10)R_C, shown in the universal covering space S³ of radius R_C. Multiple copies of the surface of last scattering (SLS) of radius r_SLS intersect in circles lying in (flat) 2-planes that are orthogonal to the plane of the page. The interiors of the circles within these 2-planes constitute matched discs. The matched-circle (observer-centred) angular radius is α. Redshifts on either matched disc increase from z_min at the centre to z_SLS on the boundary (the matched circle). The SLS can be replaced by the 2-sphere defined by z = 200 to obtain matched discs with 200 > z > z_min instead of z_SLS > z > z_min.