This flange with an O-ring seal fits the tube for the non-locking version of the 3 Watertight Enclosure. Comes with O-rings.
Boss, Face, and Flange O-Rings
BlueROV2 Underwater Vehicle Kit w/150m Tether & 4 Lights - RobotShop
Part Number X-1216-CFLS, 3/4 in. Hose ID Size and 1.88 in. Q Flange Two-Piece Fittings, Interlock Inserts, US End Configurations - O-Ring SUPERCAT 6000 PSI Flange Interlock - X Series On Kuriyama
Pentair Seal Flange O-ring for Purex C Series Pool Pump, 5-3/4 ID - 071423
P028-03-1/2 Diaphragm Kit
BX Series API Ring Joint Gaskets
O-Ring Flange (4 Series)
Customizable Cast Acrylic Tube (3 Series)
D12 Couplamatic GW Series Coupling, Extra Heavy Duty Split Flange Kits, 3/4 Flange Size
Large Coolant Flange O-ring for M57 - TuneMyEuro
BlueROV2 Underwater Vehicle Kit w/150m Tether & 4 Lights - RobotShop
BlueRobotics 3 inch エンクロージャ ロック Oリングフランジ
Ability to withstand high working pressure up to 3000 PSI (Code 61 flange). Working temperature of -40°C - +120°C. SAE J518 and ISO 6162 flange
3/4NPT SAE Threaded Flange 3000 PSI Steel ISO 6162-1 Oring Face Code 61
RX Series API Ring Joint Gaskets
1.25 BSP Threaded Hydraulic SAE O Ring Flange Adaptor Code 61 3000 Series *