MGF rear track control arm adjuster in stainless steel. 
This part replaces the stock adjuster on the rear track arm which can corrode and seizes making adjustment of the rear toe settings a problem.
They are also prone to bending if you clip a kerb!  Before dismantling the assembly check the distance between the two parts and reassemble adjusting to this dimension before having a alignment check.
Never have to worry about these seizing up again stainless adjuster and lock nuts means no more problems.
Made with a 19mm hex section making the adjustment much easier.
These were not available as a separate replacement part meaning the alternative is a complete new arm which is expensive.
Sold as a pair.