Kenwood KHS-8BL Manual page 4

3. Noise attenuating foam eartube/earplug sets can
be used to convert acoustic tube kits into noise
attenuating kits. (Option)
Take the earplug or eartube between a thumb and
finger. Gently squeeze and roll the earplug or
eartube until it is small enough to fit within the ear
canal. Position the earplug or eartube into the ear
canal. The earplug or eartube will expand to fit
firmly within the ear canal.
4. Flexible open ear inserts can be used to convert
the acoustic tube kits to allow users to hear
ambient noise through its open frame design.
(Option)