Abstract: A twist-tube for false-twist devices for texturing textile yarns is described in which the tube is provided with an enlargement, which may be at one end, formed with opposed grooves. A sapphire thread guide extends across the enlargement with its ends extending into and peripherally fitting in opposed terminal ends of the grooves. This enables a comparatively short pin to be used which is positively prevented from escaping laterally from the tube so that harmful effects of centrifugal force are avoided. The grooves may either locate the pin with its axis intersecting the tube axis or with its curved surface displaced by a fraction of the yarn thickness beyond the tube axis.