- OAO "Dorogobuzhkotlomash"
| Russia | - Obedinenie Progress, ZAO
| Russia | - Obninsky molochny zavod, OAO
| Russia | - Oboronhim, PO
| Russia | - Oboznik, ZAO
| Russia | - Obuvnoe predpriyatie "Nevel", OOO
| Russia | - Ochakovsky zavod ZHBK GAO "Mosmetrostroy", ZAO
| Russia | - Ochersky mashinostroitelny zavod, OAO
| Russia | - Odincovskaya konditerskaya fabrika, OOO
| Russia | - Odincovsky lakokrasochny zavod, OAO
| Russia | - Ohtinsky zavod poroshkovyh krasok
| Russia | - Okna Koloron, OOO
| Russia | - OKNA-PLYUS, OOO
| Russia | - OKS 01, ZAO
| Russia | - Oktava, OAO
| Russia | - Oleokam, PF
| Russia | - OLIMP IMPERIAL, OOO
| Russia | - Olivesta (Moskovsky zavod "Lakokraska") , AOZT
| Russia | - Olkom, ZAO
| Russia | - Omsktransmash, GUP
| Russia | - Oniks-3, ZAO
| Russia | - OOO "PKF Galreahim"
| Russia | - Optima - teks, ZAO
| Russia | - Opytno-eksperimentalny zavod zhelezobetonnyh konstrukcy
| Russia | - OPYTNOE-stroysertifikaciya
| Russia | - Opytny elektromontazhny zavod, OAO
| Ukraine | - Opytny mehanichesky zavod, filial AOZT "Mezhgorsvyazstroy"
| Russia | - Opytny mehanichesky zavod, OAO
| Russia | - Opytny zavod suhih smesey, AOOT
| Russia | - Opytny zavod, AOOT
| Russia | - Orel - Pogruzchik, JSC
| Russia | - Orelpishemash PKC , OOO
| Russia | - Orelstroymash, OAO
| Russia | - Orenstein & Koppel, AG
| Germany | - Oreshkinsky kombinat nerudnyh stroitelnyh materialov, OOO
| Russia | - Orgenergogaz, DOAO
| Russia | - Orgstroy, OOO
| Russia | - Orgstroyekspert
| Russia | - Orgstroysertifikaciya
| Russia | - Orgtehstroy-1, ZAO
| Russia | - Orion, NTC
| Russia | - ORLEX, ZAO
| Russia | - Orlovsky zavod "Steklomash", OAO
| Russia | - Orlovsky zavod dorozhnyh mashin, OAO
| Russia | - Orshaagroprommash, OAO
| Belarus | - OSKBES MAI
| Russia | - OST-ALKO, OOO.
| Russia | - Ostrovsky zavod elektricheskih mashin, OAO
| Russia | - Otopitelnyh priborov
| Russia | - OVESI Administracii Ryazanskoy oblasti
| Russia | - OZTP-Sarmat, OAO
| Russia |
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