kits made from one solid bar of 7075 aluminium. With holes through to tighten. 

SpigaShock extender adjustable stiffness 4 inch long £20

The SpigaShock was studied and built in solid lightened aluminum to ensure the minimum weight without loosing sturdiness. The vulcolan inside the v-bar extension provides a good vibrations absortion and can be compressed using an internal grub screw to tune the SpigaShock with the frequencies generated by every bow.

https://spigasport.com/spigashock