An assembly includes a first tube. The first tube includes a first end configured to receive a second tube. The second tube includes a first end configured to slidably translate into the first end of the first tube and to receive an insert. The insert is configured to be disposed within a first portion of the second tube that is near the first end of the second tube. The first tube, the second tube, and the insert form a seal. The coefficient of thermal expansion (CTE) of the first tube is similar to the CTE of the insert and different from the CTE of the second tube.