Captive Top Hip Flask Pewter. We offer this range of plain Pewter Hip Flasks with Captive top in a 4oz and 6oz (170 ml). This Pewter Hip flask would make a great gift as it is finished to a very high standard of British workmanship. All our Pewter Flasks are presented in a gift box including a silky draw-string bag for protection. The Hip flask has a captive top, which means it stays attached so cannot be lost. The plain flask can be engraved with a name or logo or any personal message.