After receive with your comment, I have asked to our sales explain the real need of the customer comment. And then , They would like the brake kit to support this problem first. after that the change caster is your support as the long term. So Please see as below.
-The brake kit for 150mm , 200 mm ----- 20 sets as per one size.
-And to change the caster, We will tell you in the future if we have. Right now it is not important for me to change caster. because customer tell to us about your brake kit only has broken after usage time around 2 months. That is the topic for me to tell you.
Thank you for your support