K&K Mandolin Twin internal mandocello pickup. The Mandolin Twin Internal is a fully internal pickup system. Both the transducers and the endpin-jack are mounted inside the mandolin. The transducers are attached with double-sided adhesive tape, providing a robust installation with minimum sound interference. Installation of this system should be done by an experienced luthier or mandolin tech. If you are looking for a system that is easy to install by yourself please check out K&K Mandolin Twin Fusion system.