For straining cooked fruit, I find that an ordinary metal mesh strainer usually works the best.

If the question is about raspberries and their seeds, straining is not necessary. Just enjoy them.

Here's her post on Twitter. Don't know why it came across the way it did.
"Put raspberries in pot, cooked to boil while mashing. Trying to remove seeds w/cloth strainer, not cheese cloth. HELP"

What is the product that wants to be strained and seeds removed?

Make sure they can NOT escape.

Berries? Too tightly woven cotton? Make sure they can escape, and massage or twist to exude the juices. Or give up on the cotton, and use a mesh strainer. Or, either totally or partially, give up on its being seedless. Good luck!

What are you cooking? What is a cotton straining sys? A Google search on "cotton straining sys" gives no useful results.

You will need to elaborate for people here to respond.

Que?