CA Compliant Serial Number Engraving for 100% Lowers Mailed to Us

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 We use a high power laser technology to precision engrave text to a depth greater than 0.003 inches as required by ATF's specification for serial number markings and California law. To meet ATF serial number requirements, the following information must appear:

  • Serial Number: Enter your desired serial number in this box. We recommend using less than 12 characters of text. You can use letters, numbers, or combination of both. ATF requires serial numbers to be unique for each firearm you serialize. Every serial number engraving will start with S/N: 
  • Caliber: We will mark your receiver with “Cal: Multi” as shown in photos.
  • Manufacturer’s Name: Enter the name of the person who will complete the lower. Maximum of 30 characters of text including spaces. We may have to split it into two lines of text if you exceed 14 characters. We highly recommend using your real full first and last name.
  • Manufacturer’s City and State: Enter the city and state of residence for the person who will complete the lower. Use a 2 letter state abbreviation. Maximum 30 characters of text including spaces and commas. Anything exceeding 14 characters long may be split into two lines of text.
  • Model Number: A model number is not required to be engraved except if you will be registering your rifle as an “assault weapon” with the CA DOJ. There are additional requirements for registering an assault weapon. California assault weapons must be engraved with a serial number provided by the CA DOJ. The assault weapon must have been built prior to 01/01/17. A model number must be engraved on the assault weapon in order for it to be registered as such. (Most people use “AR-15” or “AR-10” for the model number of the rifle they plan to register with the CA DOJ as an assault weapon.) If you are not registering your rifle as an assault weapon, you can make up your own serial number as long as you do so prior to 07/01/2018.

We are an FFL and can receive and ship 100% lowers.



  • The 100% lowers must be shipped back to the same exact address from which it was shipped to us. Please verify that the location you ship from will accept it in return. 
  • 100% lowers need to be shipped stripped of all parts except for the bolt catch, which can remain on the lower if already installed.  Lowers shipped to us must be shipped using tracking and delivery confirmation. 80% Arms is NOT responsible for any additional components received other than the 80% lower.
  • We do NOT engrave Polymer 80% Lowers
  • 100% lowers must be shipped using signature confirmation. Please mail lowers along with a copy of your printed order to:

80% Arms

Serial numbers are NOT required in any state that we know of, except for California. If you live in California, this product will keep your completed 80% lower legal as of July 1, 2018, when all lowers must be serialized. A more detailed explanation of this new law can be found on our FAQ page.

We do not report serial numbers or any other customer information to the government. By engraving an AR 15, you are not registering your firearm. 

Please verify the information you supply to us is correct before submitting your order. Custom engraved receivers are not returnable, and orders cannot be canceled once serial number engraving has begun. What you enter on the website is what will be engraved on your lower.

Please double check you do not have any typographical errors. 

Our lifetime warranty will cover the receiver against any manufacturing defects. All lowers will be engraved with CAPITAL letters. 

* Whether your lower is legal and/or can remain unregistered in California depends on how the CA DOJ will interpret the law, and whether you use it to build a rifle that meets the California definition of an "assault weapon". We are not lawyers and cannot provide legal advice, or warrant that our common sense interpretation of California laws will match those of the CA DOJ. We suggest you either consult a lawyer to give you a professional legal opinion or read the relevant laws yourself and draw your own conclusions. The information on our site is only intended as informal helpful pointers and is not to be relied upon as legal advice. Ultimately, nobody except the CA DOJ can predict how they plan to interpret or enforce existing legislation.