Comment: Pipe Bombs — steel or PVC pipe section with end caps in nearly any configuration are the most prevalent type of containers. Also, thick-walled cardboard is a viable non-fragmenting alternative.  source: <a rel="nofollow" class="external autonumber" href="https://2009-2017.state.gov/m/ds/rls/rpt/19726.htm">[1]</a>
<ul><li><a href="//commons.wikimedia.org/wiki/File:Pipe_bomb_01.jpg" title="File:Pipe bomb 01.jpg">Pipe_bomb_01.jpg</a>: US State Department</li>
<li>derivative work: <a href="//commons.wikimedia.org/wiki/User:Rehua" title="User:Rehua">Rehua</a> (<a href="//commons.wikimedia.org/wiki/User_talk:Rehua" title="User talk:Rehua"><span class="signature-talk">talk</span></a>)</li></ul>
<ul><li><a href="//commons.wikimedia.org/wiki/File:Pipe_bomb_01.jpg" title="File:Pipe bomb 01.jpg">Pipe_bomb_01.jpg</a></li></ul>