The GlareOne Two Side Screw Mini Male 1/4"" - Male 3/8"" is an adapter to connect a 1/4"" and 3/8"" screw hole.
The 1/4"" thread fits most cameras and camcorders, and the 3/8"" thread is typically used in tripod heads.
Due to the hexagonal shape of the middle part, the adapter can be (dis)assembled with a 13mm open-end wrench.