Etymotic Research ER38-15SM 3-Flange Replacement Eartips - Small - 10 Pack - Frost Package of 10 eartips Ear canal opening 7-11mm. Designed for use with ER4 series, HF series, MC series, ETY Kids, HD5-Safety, etyBLU, etyBLU2, HD15-High Definition Electronic Earplugs, MusicPro, Gunsport Pro, EB-15 BlastPlug, and Home Hearing Test.