CF flanges are available with tapped or untapped holes. Tapped flanges are available in UNC /UNF or metric threads. Tapped flanges have through holes, so bolts may protrude slightly from the back of the flange when fastened to an untapped flange. Untapped CF flanges can be fastened to each other with stainless steel bolts and hex nuts or plate nuts. Plate nuts center themselves over two adjacent holes and can be held in place with one finger while the bolts are tightened. They are available for most flange sizes from 1-1/3 to 10 inch ODs. As an alternative to hex head bolts, 12-point bolts are available for CF flanges from 2-3/4 to 10 inch ODs. Silver plated bolts eliminate the need for anti-seize compound in clean room environments.