Sapim Square Polyax nipples were developed for high end wheel builders. The Polyax design of the nipple refers to the rounded surface that makes contact with the rim, this angled surface ensures the spoke nipple is able to correctly align with the directional pull and load of the spoke to reduce high stresses placed on the rim, nipple and spoke and radically increase the durability and life of the wheel.
Sapim's "SecureLock" feature which is an available option prevents the spoke nipple from loosening when the wheel is under stress / destress situations to ensure that spoke tension from the day the wheel is built is better maintained throughout the life of the wheel.