The 10" APR^TM which is adjustable by adding weight discs to the external tube accessible from the front. Each APR comes with 20 45 gram weight discs.
APR Specifications (PDF).
Download Quartet10 Subwoofer Kit construction guide which uses 2 of these APRs.
Quartet10 Subwoofer Kit (PDF) This is currently not available as a separate item, only with the Quartets.
Note: For multiple items or specific locations please contact us for a shipping quotation.