16 b and 16 c is about 35 u00b0 and angle 16 u03b3 formed by inner tray rim portions 16 a and 16 b is about 90 u00b0 consequently angle 16 u03b2 formed by inner tray rim portions 16 a and 16 c is about 55 u00b0 adapted to the dimensions of the outer tray 4 see fig4 to 6 l 1 of the inner tray 6 is about 72 mm and l 2 is about 56 mm other dimensions are contemplated the inner tray peel tab 18 is arranged at the region of the inner tray rim 16 where inner tray rim portions 16 a and 16 c meet the inner tray peel tab 18 has the shape of a sickle the concave edge 18 u2032 of the sickle being joined to the outer edge 16 u2032 of the inner tray rim 16 the circumferential shoulder 22 consists of three portions 22 a 22 b 22 c corresponding to the inner tray rim portions 16 a 16 b 16 c beneath the region of the shoulder where portions 22 a and 22 c meet the bulge 24 is formed said bulge 24 has the shape of a portion of a spherical surface the convex side 24 u2032 facing the inner tray rim 16 and the concave side 24 u2033 facing the inner tray bottom 12 between the concave side 24 u2033 of the bulge 24 and the inner tray bottom 12 the curvature of the inner tray sidewall portion 14 runs parallel to the inner tray bottom 12 since both the inner tray peel tab 18 and the bulge 24 are formed away from the spouts 40 u2032 40 u2033 they do not interfere with.