In a tank for a system for injection supply of LPG for internal-combustion engines, a number of hydraulic-connection elements associated to a service flange which closes the top opening of the tank are mounted on said flange by fixing to the bottom surface of the latter, without having any parts that are mounted via through holes of the flange. The first mold assembly defines a first cavity. Polyester bicomponent continuous filaments including poly and poly having an after-heat-set crimp contraction value from about 20% to about 80% contribute to the stretch recovery properties. This step scales up a numerator for a ratio.