7 inch ID outer pipe c/w 4 inch ID inner pipe. This is a 5 foot length section that can collapse to a shorter length if need be. Pipe is very flexable,and in good condition. Not many people think to look here for materials so It is your saving. Or you could go to the store and pay 60.00 plus tax. Price includes connection rings plus springs for bends to keep the inner and outer seperate.