Glassine Envelope Storage Box for #4 & #4.5 Envelopes - Holds Over 1,000 Glassine Envelopes Glassine envelope storage box for #4 and #4.5 envelopes. Easily holds over 1,000 #4 or #4.5 envelopes. Constructed of sturdy chipboard with a black textured exterior and measures 14" x 5-1/4" x 3.5". Glassine envelopes are sold separately.