Anyone know what this is ?

[Kbrook]

I replaced a hydraulic lever and caliper yesterday ( Shimano 105) all went well but I’ve found this on the floor today looks like some sort of stopper, has a little rubber o ring. Any ideas what it is ?

 

[Oldhippy]

I'd try pulling the brakes on before leaving the building to see if hydraulic fluid leaked. That would be the only reason for the O ring unless some vindictive git at the factory just wanted to mess with your head on his last day at the factory.

 

[Sterlo]

There doesn't look to be any hole in it so would assume a bung of some description, was it in the reservoir port maybe to stop any leaking when they tested or to stop dirt getting in?

 

[I like Skol]

It's from the hose tail that comes out of the shifter, you have to remove it before joining the rest of the hose that runs from to the caliper.

 

[Ming the Merciless]

Likely sat in the calliper port where the hose now goes. It can be binned, or used as a white pawn

 

[Kbrook]

Thanks very much I’m not aware of me pulling it out of anywhere when I put the new lever and calliper on, I guess it must have fallen out without me knowing!