Our metal & plastic end caps (often referred to as spool or core plugs) are designed to be inserted through the ID of a flange and pressed into a spiral wound paper tube. The end caps have locking anchors that hold the spools simply & securely. All of our metal end caps are stamped in house and are available with custom drive holes & anchors. Need a size we don't currently offer? Give us a call and our experienced machine shop can make a die matching your requirements.