Universal Circle's Fabric

[Calcined]

Howdy I was wondering while standing in my Universal Circle. What type of fabric it is?
Does anyone of you guys know it?
I checked the page of balg.co but it did not mention it.

Edit: Its probably made of: Cotton Duck Canvas

[Lady_Eva]

@DarkestKnight says canvas, here: Material for circles

Perhaps he can also answer more.

[Calcined]

Sorry MOD, I should have used the search function. Thanks for directing me to the post.