This is the opposite of what the bottle says and what I’ve found to be true of these hubs.
The synthetic version is for synthetic fabrics that don’t take traditional dyes well. Wife and I make a loooooot of t-shirts and sublimate often enough to know which fabrics play nicely with what. Synthetic all purpose is for polyester and acrylic based stuff.
Someone on here tried to use the synthetic and it did almost nothing. All purpose is what you want, it even lists nylon on the bottle. True, it’s meaning nylon fabrics but nylon is nylon and I got perfect results using the all purpose version, doubling the dye.