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

it’s a three-quarter inch round long foam tube. Bendable. And I stuck it up under my aluminum siding that begins at the concrete block foundation because I thought maybe air was coming through making the living room cold

This is the perfect size for ear posting. I premeasure and cut about 6" pieces. The only thing I don't like is that it's packaged in a coil, so the pieces end up in a curve. You have to reshape the piece and then tape it before posting your Doberman's ears. They are lightweight and durable.

did the job

It's basically dense styrofoam with great elasticity that allows you to squeeze it into cracks. It works well as intended. It doesn't rip off easily, which is what you want.

We had an expansion joint that needed to be replaced. Whatever was used previously disintegrated and had to be removed. The gap (over 1/2 inch) was cleaned thoroughly and ready to be filled. The backer rod was easy to use. I slowly pushed it between the gap so there's a snug fit. Afterward, I squeezed self leveling sealant and it flowed smoothly across the gap.No issues with the backer rod. Just make sure it's not punctured while pushing it into the gap.

Required if the cracks or separations in the concrete go all the way through. If you don’t use it the self leveling filler will drain through the separating surfaces and will be lost.

Very good quality for stopping air flow around doors and windowes.

Good backer rod. Closed cell and dense. The correct diameter. Seems very well made. Buy and use with confidence.