position and are prevented from moving out of place until the user decides to twist the filter the bosses are made from a resilient plastic so that when the second part 3 is rotated by a user relative to the first part 2 the bosses 6 7 longitudinally compress and move out of the recesses 33 35 continued rotation then brings one of the bosses 6 7 into register with the central recess 34 once aligned the boss 6 7 resiles and snaps into position in the recess 34 causing a u201c click u201d sound as shown in fig4 when the boss 7 is in alignment with the recess 34 the boss 6 is positioned in the capsule receiving recess 26 similarly as shown in fig5 when the boss 6 is in alignment with the recess 34 the boss 7 is positioned in the capsule receiving recess 25 twisting the fluid release mechanism from the position shown in fig3 to the position shown in fig4 thus causes the boss 6 to be brought along an angular displacement path into the capsule receiving recess 26 where it contacts presses against and bursts the capsule 5 the capsule 5 is held in position by the sidewall of the recess 26 as the boss 6 presses transversely against it in this way the capsule 5 is laterally pinched between the boss 6 and.