Our innovative iON SYNC® Earthing Plugs were developed through years of dedicated research and development to create a highly durable, conductive solution for earthing-shoe enthusiasts.

Installed through the soles of shoes, iON SYNC® plugs provide a grounding experience that replicates the benefits of being barefoot.

The plugs are available in three sizes for shoe soles ranging from 4–15 mm (3/16–5/8 in.) thick. Refer to the sizing chart below to find the right size for your shoes, followed by written and video installation instructions.

Skive: If your shoe does not have a suitable recess in its outsole tread for the plug’s barb, use our skiving tool (sold separately) to remove the necessary lug and create one. Watch the video below to learn how to use the Skive.

iON SYNC Earthing Plug size chart

Base sole thickness = stack height − lug height

iON SYNC installation instructions, page 1

iON SYNC® is patented technology.

What if I can’t decide where to put the plug?

If you need help choosing the installation location or plug size, contact one of our earthing support experts and include a picture of the bottom of your shoes.

Can an iON SYNC® Earthing Plug be removed?

Yes. After removing the pull tab, press firmly against the plug’s flat barb surface from the outsole side using a medium-size Phillips screwdriver or an object of similar diameter.

Can a removed plug be reinstalled?

No. iON SYNC® plugs are designed for one-time installation. If a plug is compromised, worn, installed incorrectly, or removed, replace it with a new one.

Are iON SYNC® Earthing Plugs watertight?

When properly installed, the compression-fit rubber design forms a watertight seal against the shoe’s outsole. For the best seal:

Use the recommended plug size based on the base-sole thickness: stack height minus lug height.
Use the correct hole-punch size so the plug can compress properly.
Choose a large, flat outsole area where the barb can make uninterrupted contact.
Position the barb in an outsole recess at least 1.5–2 mm deep to protect it from abrasion, blunt force, and excessive wear.

What makes the plugs conductive?

We worked with leading polymer experts to develop a proprietary rubber compound containing a conductive filler. It creates a conductive network throughout the material that permits the transfer of the low voltages associated with earthing.

After more than 15 iterations, we developed a conductive lattice-infused polymer that balances the mechanical durability of shoe-outsole rubber with electrical resistance below 10³ ohms.

How do I determine which plug size to use?

Calculate the base thickness of your sole by subtracting the lug height from the shoe’s stack height, then refer to the sizing chart. Most manufacturers list the total stack height on the product page. Measure the lug or tread depth at the planned installation point and subtract it from that stack height.

What if the base thickness falls between two plug sizes?

Choose the larger iON SYNC® plug when the base thickness is on the threshold between two sizes.

Will I feel the plug underfoot?

If the correctly sized plug is installed in the middle of the sole and properly recessed into the outsole, you may notice it slightly at first. The sensation should normalize after approximately one hour of wear.

Do iON SYNC® Earthing Plugs work with socks?

Yes. Body weight creates contact with the head of the plug, while normal perspiration helps make the sock conductive. Our testing found a negligible difference in measurable voltage reduction between wearing iON SYNC® grounded shoes with and without socks.

How do different socks affect grounding?

The two main factors are sock thickness and the wicking ability of the fibers. Heavier socks create more distance between the foot and the plug and require more perspiration before becoming conductive.

Natural fibers generally wick well, as do some engineered synthetics. Polyester COOLMAX® and similar fibers with capillary filament profiles can develop conductive properties through perspiration.

Do iON SYNC® Earthing Plugs release microplastics?

The plugs use a food-safe polymer designed not to release microplastics into food or the environment.

Do iON SYNC® Earthing Plugs contain latex?

No. iON SYNC® Earthing Plugs are latex-free.

How does the iON SYNC® rubber plug kit compare with the Shoe Sync copper rivet kit?

Comfort: iON SYNC® rubber plugs are more comfortable.
Installation: iON SYNC® rubber plugs are easier to install.
Conductivity: iON SYNC® rubber plugs are less conductive than Shoe Sync copper rivets.

Do grounded plugs increase the risk from ground current caused by a nearby lightning strike?

Wearing iON SYNC® grounded footwear is similar to being barefoot during a storm. The plugs are designed for the low-amperage, low-voltage range associated with earthing, not the transfer of harmful electrical current. As a general safety precaution, avoid exposed outdoor areas during lightning storms.

What if it is difficult to pull the barb through the hole and seat it on the outsole?

Use a screwdriver, pen, or similarly sized object to gently pre-stretch the hole immediately before installing the plug.
Try the next larger, slightly longer plug size.
As a last resort, use the next larger hole punch to create a slightly larger opening.

Order Processing: All sandals are handcrafted in our California workshop. Orders ship via USPS within 3-7 business days.

Orders placed by Monday 7am Pacific ship Thursday.
Orders placed by Thursday 7am Pacific ship Monday.
Changes to orders must be requested within 24 hours of placement.

Domestic Shipping:

First Class Mail: $, 3-5 business days delivery after shipping.
Priority Mail (Flat Rate): $$, 2-3 business days delivery after shipping.
Priority Mail Express (Flat Rate): $$$, 1-2 business days delivery after shipping.

International Shipping:

ePacket Duties and Taxes Paid: $, 7 to 9 business days delivery after shipping.
Priority Duties and Taxes Paid: $, 6 to 9 business days delivery after shipping.
Expedited Duties and Taxes Paid: $$, 5 to 7 business days delivery after shipping.

Add 3-4 business days for the following countries: Argentina, Mexico, Vietnam, Switzerland, Israel, Portugal, Ireland and Philippines

Shipping times are estimates and not guarantees.