These are one of the custom brass inserts we supply our long time customer that had production facilities in the US and in Mexico.  We initially ran a test production cycle of 300 pieces for them to test in their assembly prior to committing for the full 10,000 pcs required in their first batch.  Plain brass material was used and the knurled outside diameter was set at .235".  Our customer was in a rush and we ran an expedited option with lead time at under 2 weeks.