Integrated into many of the flagship storage containers made by Thermo-Fisher Nalgene®, the 83B “buttress” thread has a heavy-duty thread finish -- more robust than many ISO or DIN standard threads of similar dimension.  For this reason, it is often found on wide-mouth lab bottles due to its resilience during autoclaving.

The 83B caps provided here will also fit Foxx Life Sciences™ and Kautex® brands of the same thread type.