Actually, I think you are looking for: 

EV3 Technic Ball Pivots
5003245, $15 for a set of 2
https://shop.education.lego.com/legoed/en-US/catalog/product.jsp?productId=5003245&ProductLine=LEGO+MINDSTORMS+Education+EV3

On Sun, Sep 27, 2015 at 12:00 PM, Mahesh Rachakonda <[log in to unmask]> wrote:
We purchased on eBay. Search for "ev3 metal caster".

Best,

Mahesh

On Sep 27, 2015, at 11:56 AM, Ruchir Ghosh <[log in to unmask]> wrote:

Hi

I am looking for the roller ball with the holder that acts as rear wheel for Robot while in motion. Can anyone suggest from where I can get those. I believe they come as a part of extended kit sold by First. Unfortunately I cannot find this piece and wondering if anyone can provide some info as from where I can get this quickly.

Appreciate any help you can provide.

Thanks
Ruchir


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