Fantasea Step ring from 55mm to 67mm
This adaptor convert a 55mm thread to 67mm thread.
Particularly the 55MM thread on the FRX-100 III and Fantasea FRX-100 IV is it useful. Then 67mm wetlenses can be used. Both macro wetlenses and wide angle wetlenses.
Alu ring - can be used in salt water. Don´t forget to rinse it after use, and take it of the wetlens after use.