[s-cars] Broken plastic nut on 993 caliper... what is it?

[Scott Munger]

ECS stage 2 brakes are getting installed tomorrow.  I was inspecting the
calipers and found a broken piece on one.  There is some blue plastic
material... Is this a plug for the lines to go in and it doesn't matter if
it's broken?

http://www.npgcable.com/~mungerts/urS4/brakes/broken-plastic-nut.jpg


What is it?  What can I replace it with?

TIA (sorry in advance if it's a dumb question :-\ )
--Scott Munger
'93 S4
'97 Cabriolet