SC Protium Reservoir Retention Ring – Black set of x2 RRB-000-60 Protium Reservoir Retention Rings come included with Protium Reservoirs and one comes included with Protium D5-Reservoir Combos. This is a set of two retention rings which you can purchase separately in case you would like to change the color of your Protium Reservoir Retention Ring/s. Specifications: Protium Reservoir Retention Rings: 6061 Aluminum, CNC Machined, Anodized, Black. x1. Installation: For standalone use of the Protium D5 Pump Top without a reservoir. The lid mounts via the thread onto the top of the pump top. Make sure to use the O-Ring which was included with your Protium D5-Reservoir Combo or Reservoir.