Robinair's No. 16913 Replacement Sample Filter is a genuine Robinair replacement part for the Nos. 16900 CoolTech ID and 16910 CoolTech ID Plus Refrigerant Identifiers. The purpose of the sample filter is to provide retention of particulates and oil mist suspended within the sample vapor. Filter incorporates a red dye that indicates when replacement of the filter is necessary. As soon as red spots or discoloration begin to appear anywhere on the white outside diameter of the filter element, THE FILTER MUST BE REPLACED. Sold individually. Robinair, a Bosch Automotive Service Solutions brand, is a global leader in service tools and equipment based in Owatonna, Minnesota. Robinair is recognized throughout the world as the quality and performance leader in AC/R evacuation tools and this position has led to its success with the full range of products that serve the heating/ventilating/air conditioning/refrigeration (HVAC-R) and mobile markets.