The I-485 is the Application for adjustment of status. The I-751 is the petion for Removal of Conditions. K visa holders must file the I-485 to adjust status in the US, and then file the I-751 to Remove Conditions. CR-1 and IR-1 visa holders adjust status in China, and will be mailed a green card shortly after their arrival in the US. For CR-1 visa holders who wait until AFTER their 2 year wedding anniversary before entering the US, and IR-1 visa holders, the green card is an unconditional (10 year) green card. CR-1 and IR-1 visas are identical, except that if the visa interview occurs after the second wedding anniversary, the IR-1 visa is given. The I-751 is filed within 90 days of the expiration date on the green card to remove conditions. This step is not necessary for those with an unconditional green card.