Tap to change same texture of two different objects

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Hi guys, I am relatively new to Lens Studio. I am making a Snapchat filter using the wrist tracking template. I have created 10 different textures for the face of the watch. I am able to switch between these textures by tapping on the screen but only for a single hand.

What should I do such that whenever the user taps on the screen, the texture on both hands switches to another texture? I have created 10 materials & I am using the same materials for both hands.

Let me know if you need further clarification. Thank you in advance for the help