Printmaster White w/ Blue Security Tint Envelopes – #10 Window (4 1/8 x 9 1/2) – 24lb Writing Wove – 500 per Box. Printmaster White w/ Blue Security Tint Envelopes – No. 10 Window (4 1/8 x 9 1/2) – 24lb Writing Wove – 500 per Box.