Dental X Ray Phosphor Plate Barrier Envelopes Size #0 #1 #2 100pcs/Box. AZDENT unique Barrier Envelope design allows the package to tear open in a direction that minimizes cross-contamination through the innovative Y-notch design. Defense from contamination provided by the envelope allows PSP sensors to be reused. Black opaque envelope back prevents ambient light exposure resulting in distorted images. The X ray barrier envelopes are cost-effective and easy-to-use which allow you to save both time and money.