SIKA Closed Cell Foam Backer Rod, Gray, 3/4″ Diameter x 20′ Long, Water-Resistant Joint Filler for Sealant Application, Flexible and Durable for Cracks and Joints

Customers find the backer rod effective, with one mentioning it works well with concrete caulk. The product receives positive feedback for its quality, ease of use, durability, and value for money. They appreciate its dense foam construction, though opinions about size are mixed, with some finding it good while others say it's too large.