Office Depot #10 White Right Window Envelopes For Insurance Claim Form 500-BX, right window envelopes for use with HCFA 1500 Medicare Claim Forms. Security-tinted inside for privacy and confidentiality. Made of 24 lb white wove, Office Depot medical claim white business envelopes (#10) offer a substantial feel. Office Depot medical claim white business envelopes come in a box of 500, so you have plenty on hand.