Excalibur 1596PF SportPro Defender is a first down grey underbase or a last down backer for cold peel transfers to block dye molecules in 100% polyester dark colored garments that are prone for dye migration. The proprietary particles contained in Excalibur 1596 SportPro Defender act as filters to filter out dye molecules which can migrate up through the ink film during the curing or heat transfer process. Excalibur 1596PF SportPro Defender prevents dye migration on many 100% polyester fabrics where normal low-bleed plastisol inks fail miserably.