Anybody using one? What’s the shape similar to? Durable enough for MTB use?

Yes, similar to the Charge Knife but comfier and yes, durable enough for MTB. I’ve used mine on the road bike, but after much deliberation its not right for my backside.
If you want one in black cheap in great condition send me an email!

I tried one on road bike but it came up quite narrow and wasnt that comfy so I moved it on. Ive put a Scoop flat on and thats much better for me.