Secreted protein that is involved in larval elongation, early adult growth and male tail development. Expressed in the hypodermal regions hyp4 and hyp7 from the comma stage of embryogenesis and subsequently throughout development. Mutants display an increased body growth rate during larval development and male tail morphological defects characterized by thickening of the male rays, with rays 5 and 6 the most severely affected in most cases. RNAi-mediated knockdown results in increased body length.