GSA eBuy RFQ -- Limited to SIN Vendors? I posted a RFQ on GSA e-Buy recently, under SIN 899-1 (Environmental Services), released to all 667 SIN 899-1 schedule contractors (we don't have a preferred source and we're really interested in competition) -- a firm asked me if it could provide a quotation even though its schedule wasn't listed under SIN 899-1 -- I haven't faced this question before, and I can't find a good answer in FAR Subpart 8.4. Is a RFQ citing SIN 899-1 open to all GSA schedule contractors? Or only those who are listed under SIN 899-1? This is a requirement for services requiri