# Biological products exceeding 4 liters or 4 kg containing Category A — Postal shipping restrictions by item category

For Biological products exceeding 4 liters or 4 kg containing Category A, carrier is USPS; restriction type is prohibited; scope is all mail; conditions is Biological products, cultures, or specimens known or suspected to contain Category A infectious substance, or exceeding 4 liters/4 kg limits, are nonmailable, recorded from its source on 2026-08-04.

- **Item category:** Biological products exceeding 4 liters or 4 kg containing Category A
- **Carrier:** USPS _(our reading, not quoted from the source)_
- **Restriction type:** prohibited _(our reading, not quoted from the source)_
- **Scope:** all mail _(our reading, not quoted from the source)_
- **Conditions:** Biological products, cultures, or specimens known or suspected to contain Category A infectious substance, or exceeding 4 liters/4 kg limits, are nonmailable

## What the source says

> Biological Products and Specimens: Biological products, cultures, stocks, or other biological specimens known or suspected to contain a Category A infectious substance. Mailpieces exceeding 4 liters (1 gallon) for liquids or 4 kg. (8.8 pounds) for solids are nonmailable.

## Source

- https://pe.usps.com/text/pub52/pub52c3_025.htm

Last verified: 2026-08-04. Review by: 2027-08-04.
Part of [Postal shipping restrictions by item category](https://referencesource.org/shipping-restrictions-by-class/).