This is a scuba diving mouthpiece. Currently sold at MIC21 for 6,688 yen (tax included). I mistakenly purchased it for the wrong regulator manufacturer, so it's being sold unused. The following is a quote from the product description: "Because you can mold the part of the mouthpiece that you bite on to fit your teeth, you won't have to clench your jaw, and the burden on your jaw will be reduced♪ Molding method is easy♪ Just soak it in hot water for about 30 seconds and bite down! [Compatible Manufacturers] Inner diameter 28.6 x 12.7mm Apollo Sports Aqualung / US Divers (metal models) Atomic (models before 2004, check required) SAS NDS Bism, Beuchat (Evolution, Iceberg & Nitrox, VXT8, VXT Octo, VX4, VX80) Cressi-sub (excluding Ellipse) Dacor (models after 1992) IST (excluding Proline) OCEAN MASTER PRO SUB (Avalon) Scubapro (all models up to 2009) SEAC Sherwood (most old models, Brut, Shadow, MagnumII, Oasis, Blizzard before 1991) SPARE AIR SUBGEAR TUSA (excluding Imprex) #scubadiving #scubadiving #diving #regulator #reg #mouthpiece #octopus #diving #divingmask #scuba #scubadiving #TUSA #Tusa #snorkel #snorkeling #marinesports #fins #strapfins #skindiving