Model 1691 Portable Expander Just wheel in the 1691 to the job and put Huth's expanding power to work. Quickly and easily size muffler nipples and pipes anywhere in your shop. The 1691 comes with the tooling shown above for expanding capacity from 1-1/2" to 3-1/2". Additional tooling gives you expanding capacity form 1" to 5-1/2".