Acrylic keychains have a protective film on both sides. 
Peel off the film on the printable side before printing, then peel off the other one after printing.
 
Material: Cast acrylic
White sublimation coating on one side
Key ring included.
 
Pressing Recommendations (each press is different. See what works best for your particular press):
DO NOT mirror your image!
Temperature: 360 F
Time: 80 seconds
Pressure: low.