There are several different series for Lenovo Thinkpad X1 Carbon laptap. Please make sure which Gen your laptop is.

This batterydoesn't fitThinkpad X1 Carbon Part Numbers:00HW002 00HW003 SB10F46440 SB10F46441
Note:
Please check carefully about your laptop model name/battery part number/battery shape and size to make sure you purchase the correct battery.

How to confirm that the battery is suitable for your laptop?

Method 1: Use System Information to find your laptop model

Step 1: Press Windows + R to open Run window.
Step 2: Input "msinfo32" in the empty box and click OK to open System Information.
Step 3: Keep in the System Summary section, and you will find the System Model item in the right pane.

Method 2: Remove Battery from Laptop to find your laptop battery part number

Step 1: Switch off the laptop and unplug the power cable in case of electric shock
Step 2: Remove the back panel with the screwdriver. You should to this with care avoiding any harm to the laptop components.
Step 3: Disconnect the cable connected to the battery and then take out the battery. After that, you can check the specifications of your battery.