[フィッシュアイ] FIXリングディフューザーTGの買取情報

The item you're referring to is the Fisheye FIX Ring Diffuser TG, designed for use with specific underwater cameras, most likely the Olympus TG series, including the TG-6. The ring diffuser helps to soften and spread the light from underwater flashes, resulting in improved lighting for underwater photography.
The note indicating that the TG-6 and PT-059 are sold separately suggests that this diffuser is an accessory intended to be used with those specific models for enhanced performance while shooting underwater. If you have any specific questions or need more information about this product, feel free to ask!