Fair question! Before we started 3D printing, we did not own calipers either. Calipers are a measuring device and can be purchased for under $10 online or under $20 at big box home improvement stores. They are incredibly handy to own as a peptide enthusiast. There is rarely standardization in vial sizing across various manufacturers - for example, a box advertised as a 10ml box may not actually fit your specific 10ml vials. Any responsible vial box maker will require you to provide caliper measurements on custom box requests, so do yourself a favor and buy a pair!
