This is a transforming neck unit for Titans Return Galvatron, designed to remove the Titan Master function and instead swing the head into the body cavity. Cannon mode is unaffected, and the jet mode only suffers from the nose pointing slightly down.
This kit was designed to work with the head I've created here: https://www.shapeways.com/product/749KJ6CJV/alternate-head-2-0-for-titans-return-galvatron
However, it should also work with the figure's original head by replacing Nucleon's head, and it may work with other head kits designed with the same ball size.
Also check out my back spike replacement here: https://www.shapeways.com/product/42VETLCH6/back-spike-thruster-for-tr-galvatron?optionId=61842014&li=shop-inventory
And Fakebusker's cannon adapter here: https://www.shapeways.com/product/GSQEY76EM/tr-galvatron-cannon-adaptor?optionId=60260517