Children under the age of three have a tendency to put everything they can into their mouths. As a parent or caregiver, keeping them from putting something in their mouth that they can choke on is a major challenge. Granted, most toys come with appropriate age levels noted on the label; but if you live in a home with an older child, you might have a wide variety of toys in various sizes and no packaging to tell you if they are age-appropriate for your infant or toddler. There are commercial choke testers you can purchase, but you can make one at home for a fraction of the price.
Get an empty toilet paper roll. This is as simple as waiting until the next time you run out of toilet paper and saving the roll instead of throwing it away or recycling it.
Take a small toy and see if it will fit through the toilet paper roll. The size of most commercial choke testers is 3.5cm. The size of most toilet paper rolls is 4.5cm, so you are being in a way overcautious by taking this approach as you will have some toys that you will reject as unsafe that a commercial tester would find safe.
Give the toys that do not fit through the toilet paper roll to your child.
Latex balloons are larger than the toilet paper tube while inflated but should never be given to a child under three because, if they pop, they pose a choking hazard.