Fastener Sizing Guide

Follow the four step process below to determine the fasteners to use for your vehicle.  Do this both for your rear license plate and, if applicable, your front license plate.

Step 1

Pick Bolt or Screw


Bolts are used where there is a metal nut that the bolt can screw into. They can also be referred to as 'Machine Screws'.


Screws are used where the screw goes into plastic (either onto a mounting plate or directly on the plastic car bumper). They can also be referred to as 'Self tapping screws'.

Step 2

Pick head size

Narrow Head

Narrow head size fasteners are 12mm wide and are designed for plates/frames with circular holes where the head will completely cover the hole.

Wide Head

Wide head size fasteners are 16mm wide and are designed for plates/frames with elongated holes where the head will completely cover the opening.


Step 3

Pick thread width


Bolts must match exactly the thread width and thread pattern of the nut they go in.

Our bolts are metric sizing of M5 (generally works for BMW rear plates - note around 2020 BMW switched to using screws for rear plates) and M6 (generally works for Audi/Mercedes rear plates).

Metric bolts will not work on imperial sized nuts.


Since screws go into plastic, there is some leeway on the width.

Our screws are M5 or M6, please ensure the width of the current hole in the plastic the screw will go into is able to able to accommodate the screw size.  The diameter of the hole in the plastic must be smaller than the diameter of the screw in order for it to have something to grip onto.  If a larger diameter screw was previously used, it is not possible to use a smaller diameter screw as it will not grip.  Most import cars that use screws will use M5 screws.  Most domestic cars that use a 1/4 inch wide imperial screws can substitute a M6 screw.  

If there is no hole in the plastic, a pilot hole using a 1/8 inch drill bit is recommended. 

Step 4

Pick thread length

Thread length is dependent on how much depth there is for the screw/bolt to go into.

This will vary with:

Thickness of the license plate

No frame, thin frame, thick frame

General Guidelines

No frame / thin frame
Thick frame

For plates that mount onto a backing plate which then mounts to the bumper, ensure you choose a fastener length that does not protrude past the mounting bracket otherwise there is a risk the tip of the fastener will pierce the underlying bumper.