Unknown part in rear brake system

[ladderboy 0]

Can anyone help me identify a part? Where the rear brake pipes turn to go from outside to inboard part of car, in front of the fuel tank, on either side there are large (very rusty!) cylinders, approx 2 cm diameter, 6cm long. Are these purely connectors between 2 sections of solid brake pipe? They seem ridiculously large, heavy and (rusty!) if that's all the are.......  Suggested replacements? 

[Anthony 1,000]

They're the rear brake compensator valves on 1.9 GTi models.

[Leslie green 81]

Despite being rusty they should be work fine , you could clean them up and paint them 

[Richie-Van-GTi 70 2 Cars]

Still readily available online if hey are knackered, but rarely fail