my sons hat is 66% polyester 13% acrylic 8% rayon 6% nylon 5% cotton and 2% wool
Does it need to be checked or can it be worn since it is only 2%
The fact that it is only 2% wool will not automatically dismiss any issue of shatnez, because if there is even one thread of wool, it is not botil and exempt from being shatnez. However practically it could be that I doesn’t contain any linen, however this you would have to ask a shatnez tester.
Best wishes and have a healthy winter.
Rema Y:D 299-1.