Because the California Universal only fits about 95% of masonry chimneys in California, Chimney Products has some caps to fit the remaining 5%. the most popular (most used) is the 13"x13" which fits down to 8"x8" and everything in between (like 9", 10", 12" and 13" masonry rounds). They are constructed with the same quality materials as the California Universal with 5/8" mesh, and installs the same way. The packing is a little different because of their size--you can get them shipped in either a single or 5-Pack. Great for the S.F. Bay Area's patent chimneys and those concrete "tilt-ups".