1.   But as manufacturers have made the walls of hollow aluminum bats thinner to make the bat lighter, aluminum bats are cracking and denting much more easily.

2.   But it is only a hollow aluminum shell.

3.   It was a hollow aluminum pillar with a layer of soft lead and a steel stylus attached to it so people could write into the pillar.

4.   The pieces of structure are mostly hollow aluminum.

5.   Their shared characteristics include a conical indentation roughly five feet long and arcs and spirals of hollow aluminum pipe about eight inches in diameter.