The most common and cheapest choice is standard 2mm Float Glass but in some situations you may want to choose a different option to protect your artwork.
Acrylic or styrene is becoming a popular choice if your artwork is very large or weight might be an issue. In addition, these glass alternatives are less likely to shatter so are the best choice if the frame is to be shipped.
Non-reflective glass has a single side etching which reduces the glare produced by the reflection of direct sunlight.
UV filtering glass is the highest quality and is popular with museum and industry experts. It is used to prevent fading and reduce reflections and is also scratch resistant.