According to the product description, I think they were up to 2.5 cm high. We have some with a height of up to 4 cm.
There are good web services especially for this, where you can buy the appropriate bars so that the robot can get over them.
We got ours from https://www.helpyourrobot.de/.
They have a good website, fast delivery and the products came out nice. I can recommend them.