New Age Fireplace Chimney Outer BlocksNew Age chimney zero clearance is a 2 piece system with a separate outer block and clay inner liner. When ordering, choose 1 clay inner liner per 12 of required chimney height, and 1 outer chimney block per 8" of required chimney height. Clay inner liners should protrude approximately 4" above the outer chimney block at the top of the finished chimney. NA36 Fireplace uses 23" x 23" (SA2323 8) Outer Block NA42 Fireplace uses 22" x 26" (SA2226 8) Outer