TPMDs are used whenever the standard metering tips are incapable of reaching extremely low dilution rates.  For example, the MixMaster systems can't go any lower than 1:256 on the quart-fill side and 1:512 on the bucket-fill side.  When you need dilution rates lower than that, you need TPMDs, also known as "knuckles."

We carry three:

The 3 knuckle TPMD is used in quart fill MixMaster systems to achieve a 1:512 dilution. This allows the preparation of sanitizing solutions of products such as First Mate Concentrate and Tric without the use of a metering tip.

The 1 knuckle TPMD is used in bucket fill MixMaster systems to achieve a 1:750 dilution. This allows the preparation of sanitizing solutions of products such as Proxy without the use of a metering tip.

The 1/2 knuckle TPMD can be used to reach other dilution rates that are desired.  See instructions in the downloads section.