Abstract: Flow block (1), intended for a fiberizing installation and for receiving molten material, comprising a single cavity (10) which has a flow channel (11) bounded by a wall (11a). The inlet orifice (12) has a shape which is asymmetrical with respect to the mid-plane (Y) of the block extending along the shortest extension and has an upstream part on the glass inflow side which is wider than its opposite downstream part with respect to the mid-plane. Furthermore, the slope of the wall (11a) on the upstream side is advantageously steeper than the slope of the downstream side. The invention also relates to the bushing block, which is very squat compared with the flow block.