These cover sheets for use with heat press material are critical, especially when decorating 100% polyester. These sheets will protect the fabric as it can turn glossy wherever the heating element or non-stick cover sheet touches it. Multi-Purpose Cover Sheets will also leave more of a matte finish on the print.
You cannot use a typical Teflon cover sheet on slick 100% polyester without leaving the impossible-to-fix glossy square. This cover sheet is a far better option. Simple keep your pressure and heat to the minimum and you should avoid heat damage while using these sheets.