that precise alignment of the ribs and channels prior to sliding the core onto the spindle 12 is not necessary when fully inserted onto the spindle 12 the ends of the ribs 30 a f engage the stops 60 as illustrated in fig3 when the core 10 is inserted onto the spindle 12 the inner edges 32 of the ribs 30 a f are spaced from the first exterior surface 42 which defines the base of each channel 58 thereby leaving a space 62 between each inner edge 32 and the first exterior surface 42 the spaces 62 allow the core 10 to contract or compress radially when used ribbon 14 is wound onto the core 10 the size of the spaces 62 is chosen so that at the maximum anticipated extent of contraction of the core 10 the inner edges 32 remain spaced from the first exterior surface 42 therefore when the core 10 is contracted there is no contact between the inner edges 32 and any exterior surface portion of the spindle 12 as a result as the core 10 is contracted radially by the ribbon 14 the core is not squeezed onto the spindle 12 when it comes time to remove the core from the spindle the core slides off.