Abstract: A reblow former for use in the manufacture of moulded construction products from dry particulate materials is proposed which includes an elongate body part (11) and an inflatable elastomeric sleeve (14) disposed about the body part, the body part having ribs (12) thereon to provide an indented transverse profile and the sleeve (14) having a transverse perimeter length which corresponds to that of the body part (11) and lying in intimate surface contact with the body part (11) in the non-inflated condition thereof. The transvere perimeter length of the sleeve (14) in the unstretched state thereof approximates to the transverse perimeter length of a core void (15) into which the reblow former is inserted such that, on inflation, the sleeve (14) is brought into contact with the core void surface of the core with not material stretching of the material of the sleeve.