Abstract: Preforms 1 for the manufacture of synthetic bottles are transported along a conveyor track 10 formed by two parallel slide-rails 11 arranged such that a perpendicular common to the two slide-rails is substantially horizontal. The preforms have heads 2 larger than their bodies 5, and are vertically supported between the two slide-rails by their heads. The conveyor track embodies unbalancing mechanism 14 in the form of a raised and arcuate rail section 15 for tilting interlocked preforms 6.sub.1, 6.sub.2 such that their center of gravity G is shifted outside of one of the slide-rails 11, whereby they become unbalanced and fall off the slide-rails. An extractor 17 formed by a pair of counter-rotating, bladed wheels 18 may also be provided, for grasping and lifting off vertically oriented interlocked preforms.