Contact – STX Process Equipment, L.L.C. Contact us to see how we can meet your needs. Mailing: PO Box 538. Physical: 4819 Hwy 44. Freer, Texas 78357. Office (361) 394-1400 / Fax (361) 394-7135. FIRST NAME. Contact us to see how we can meet your needs. Mailing: PO Box 538. Physical: 4819 Hwy 44. Freer, Texas 78357. Office (361) 394-1400 / Fax (361) 394-7135. FIRST NAME.