Bose identifies this as the QuietComfort 25 headphones ear cushion kit and says it replaces cushions for QuietComfort 25 headphones; it is sold as a pair.
The manufacturer says the pads are designed for the listed Bose models, including QuietComfort 25, and claims they help block noise; it also notes that replacement pads can sometimes change noise cancellation or audio quality. No QC25-specific measured ANC result is provided.
The page says the pads are sold as a pair and claims they conform to the ear and block noise. Its FAQ cautions that replacement pads can sometimes affect noise cancellation or audio quality; it provides no QC25-specific measured ANC result.