Constructed of glass-filled nylon, these units have positive up-and-down locks, ... Constructed of glass-filled nylon, these units have positive up-and-down locks, a smooth, dependable cam operation, and a tempered-steel, 3/32' (2.4mm) wire strut. The 1-oz (28.4 grams) micro retracts can be operated with standard or retract servos. Recommended for up to 5lbs (2268g) model weight.