Container preform made of plastics material

A mold for forming a preform, the mold comprising at least a mold body comprising:

• a lateral wall with an impression of an outer face of a body of the preform;
• a mold base comprising an impression of an outer face of the base of the preform;
• and
• a core comprising an impression of an inner face of the preform;
• wherein the preform comprises:
• the body, the body being rotationally symmetrical about a vertical central axis, the body having an outer wall and an inner wall, a radial distance between the outer wall and the inner wall defining a wall thickness;
• an open neck that extends as a continuation of the body from an upper end thereof, the neck being separated from the body by an annular collar;
• and
• the base, the base closing the body from a lower end thereof, the base being rotationally symmetrical about the vertical central axis;
• wherein the body has a substantially cylindrical shape in which a wall thickness increases from the collar towards the base over a variation height Hv that is strictly less than a height H between the collar and the lower end of the body strictly greater than 0.35 H, the variation height Hv being a mean of the variation height Hv1 of the outer wall and the variation height Hv2 of the inner wall, and
• wherein a first wall thickness E2 under the collar increases over the height Hv and wherein the thickness of the wall of the body between the height Hv and the lower end of the body is substantially constant and equal toa greatest thickness E1 of the wall of the body at the variation height Hv1 or the variation height Hv2.