Abstract: A spool wrapped with a covered fuze delay wire in which accurately predicle delays are obtainable and adverse relative or slippage motion between the wire and the spool flanges is precluded, especially during operative burning of the wire. The fuze wire passes through and is secured to the spool flanges by means of heat shrunk tubing elements abutting the opposed faces of each spool flange and containing a silicone rubber strip in which are embedded uncovered wire portions. The heat shrunk tubing is of silicone rubber material to insulate the uncovered wire portions from the spool.