12" Clay Thimble 7" x 12" Catalog Chimney Items 12" Clay Thimble 7" x 12" SKU : 712CT Description Concrete Chimney Block | NYS Tek Spec 3.5 | Heat Stop Refractory Appx. Inside Dimension: 7 1/4" Appx. Outside Dimension: 9" Size: 7" x 12" Spec Sheet Rates Please contact us for current pricing and availability. Request Availability