The plastic does it's job in allowing you to move freely but the problem I noticed is if I sit too long in one position little divots form in the plastic and I am almost stuck in a pothole. It's the quality you get at the price you want to pay. That being said the plastic is not thin or flimsy so if you're more up and down than this might work for you.
Excellent quality; a bot more pricey than competitor yet I feel the quality i.e. sturdiness and fit is very good. The ordering was easy and delivery was w/in two days. All great!