SupremeX Old Style T4 Window Envelopes - #10 - 24lb White Wove - Security Artline - Window - 4-1/8" x 9" - 500 PackOld style for sending out T4 envelopes prior to the new size of 5 3 4" x 9". This white wove business envelope provides ample space for custom labels, stamps or print on the front of the envelope. The added security tint for this envelope provides added privacy and the clear poly window allows for easy view of addresses.