The outside width of the plastic holder measures 4.5” (not 4”). The useable depth of the plastic holder (top to bottom) measures 3”. The CDC COVID vaccine card I received measures 4.75” x 3.5” (before trimming). The holder may be useful for smaller paper cards. Sturdy product. Provides good protection.

https://www.amazon.com/Vaccination-Protector-Immunization-Waterproof-Resealable/dp/B08YXDHK9V