CERTAIN HOPKINS TAP BREAK-AWAY SWITCHES. THE PLUNGER PIN SOLD SEPARATELY AS MODEL NUMBERS 20009 & 20012 AS WELL AS BEING INCLUDED AS A PART OF VARIOUS BREAK-AWAY KITS WITH THE FOLLOWING MODEL NUMBERS: 20001, 20002, 20003, 20004, 20005, 20010, 20014, 20019, 20099, 20100, 20102, 20103, 20300, 20303, 17120009, 1170200001, 1170200005, 1170200099, 1530200003, 1530200004, 1540201000, 1550200003, 1580200004, 1590200004, 1610200003, 1700200003, 1770200003, 1800201000, 7020200001, 7020200002, 7020200003, 7020200004, 7020200005, 7020200009, 7020200010, 7020200012, 7020200013, 7020200099, 7020201000, 7020201001, 7020201002, 7020201003, 7020201004, 7020201007, 20005A, 20009A, S2000L, S20002, S20003, S20005, S20009, AND S20099. IF THE O-RING IS NOT PROPERLY SEATED IN THE GROOVE PROVIDED, THE RESIN PLUNGER PIN COULD BE PLACED UNDER CONTINUOUS TENSILE LOADING CONDITIONS. THIS COULD RESULT IN STRESS CRACKING OF THE PLUNGER PIN OVER TIME.