Most important is that in a four-roll machine it is possible to produce a complete ring (or any other shape) in one single pass. Also, a four-roll design can clamp the profile more securely and manage bending moments more precisely than three-roll machines. This gives better control over curvature, produces more accurate geometry, and supports stable pre-bending — all of which contribute to consistent results especially in aluminium profiles that are sensitive to uneven pressure.