Dawn,
There are two places to adjust your length.
1) The tenon you turn on the top can be 1/4" to 3/4" long (1/2" of adjustment).
2) The "indent" in the bottom that accomodates the hardware also has about a quarter inch of flexibility - if you use my router method of creating this, it is easily "depth adjustable".
Having struggled with this for MANY mills, I now purchase (and sell) only 10" and 18" mechanisms, then cut them after the mill is finished to fit THAT mill. MUCH easier!!!!![
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And, yes, I do have some salt mechanisms, send e-mail for further info.