How to Fit a Prong Collar: Sizing and Fitting Guide

Short answer: choose the wire gauge by your dog's weight, not its neck size. Measure the neck high up, just behind the ears, then add or remove links until the collar sits snugly in that position without pinching. Fit it high behind the ears and under the jaw, never low on the neck, and only use it on a lead during training sessions.

Last updated: 8 November 2026
Written by the K9 Store team, which includes World and National Champion trainers

Our team includes World and National Champion trainers, and in our experience poor fit is a common problem with prong collars. A collar that is too loose slides down the neck and works on the wrong part of the dog.

One that is too tight presses all the time. This guide takes you through gauge, measuring, links, fastenings and covers, using Herm Sprenger's own guidance.

On this page

• Step 1: choose the wire gauge by weight
• Step 2: measure the neck in the right place
• Step 3: set the length with links
• Step 4: fit it high, behind the ears
• ClicLock vs standard fastening
• Rubber tips and prong covers
• Stainless or black?
• Responsible use
• Shop the kit
• FAQs
• Need help with sizing?

Step 1: choose the wire gauge by weight

Herm Sprenger sizes its prong collars by wire gauge (the thickness of the wire in millimetres). Each gauge also has a fixed link size.

Sprenger says to pick the gauge for your dog's weight first, then set the length with links. Sprenger says that using a gauge not designed for your dog's weight voids the warranty.

Weights are Sprenger USA's figures converted to kilograms and rounded. Our product listings use the same figures: 2.25 mm for dogs up to 18 kg (40 lb) and 3.2 mm for dogs up to 40 kg (88 lb).

Trainer tip: if your dog sits between gauges, ask us before you buy. A heavier gauge also has longer links, so it can sit less closely on a slim neck.

Step 2: measure the neck in the right place

Measure where the collar will sit, not where a flat collar sits:

1. Use a soft tape measure or a piece of string.
2. Place it high on the neck, right behind the ears and under the jaw.
3. Pull it snug, but so you can still slide one finger underneath.
4. Note the measurement. For a prong collar with an assembly chain, Sprenger suggests adding about 5 cm (2 in) to choose the starting collar length.

Sprenger collars come in a standard starting length for each gauge. For example, its ULTRA-PLUS collar with assembly chain is listed at 41 cm in 2.25 mm and 58 cm in 3.2 mm.

You then shorten or lengthen it with links, so you are buying the gauge first and adjusting the length after.

Step 3: set the length with links

To shorten the collar, squeeze two neighbouring prongs together and unhook one link. To lengthen it, add an extra link in the same gauge. Links must match the wire gauge of your collar, so a 2.25 mm link will not fit a 3.2 mm collar.

Each link changes the length by its own link size (3 cm on a 2.25 mm collar, 4 cm on a 3.2 mm).

Trainer tip: when the fit is right, the collar sits close all round the neck and does not hang in a loop below the jaw.

Extra links cost £2.99 (2.25 mm) and £3.99 (3.2 mm) at the time of writing.

Step 4: fit it high, behind the ears

The right position is high on the neck, just behind the ears and under the jaw. Sprenger's own guidance says prong collars "must be fitted closer to the ears". In practice:

• Open a link to put it on. Sprenger notes that a collar without a clasp is opened by pinching at a middle link. Unhook it, place the collar round the neck and hook it back together.
• Centre plate. Sprenger's centre plate is designed to relieve pressure on the larynx. Trainer tip: keep the lead rings on top of the neck, behind the ears.
• Clip to the right ring. On collars with two fixed rings, clipping the lead to both gives a centred, more even action.
• Check the snugness (trainer tip). You should be able to slide a finger under the chain. If the collar drops down towards the shoulders when your dog moves, it is too loose. Take out a link.
• Use a backup. Sprenger recommends a safety clip or a flat collar as a backup in case the prong collar comes undone.

ClicLock vs standard fastening

Prices at the time of writing. Sprenger calls the ClicLock its most recommended clasp. You still size the collar with links first; the buckle just saves you opening a link every session.

Sprenger also makes the NeckTech Sport, a discreet collar with 3 cm-wide links and inward-curved, rounded prongs. We stock it in 48 cm and 60 cm with a ClicLock, and as a carabiner version with an assembly chain.

Rubber tips and prong covers

Covers fit over the prongs. Trainer tip: covers are worth considering for thin-coated or sensitive dogs. We stock a prong collar cover for 3.2 mm collars (£11.49 at the time of writing).

The Schweikert collar cover is a 45 mm webbing collar with hook-and-loop fastening. Schweikert designs it for e-collar receivers, so ask us before using it with a prong collar.

Whatever you fit, check the neck after each session for rubbing or marks.

Stainless or black?

Both are stainless steel. Sprenger's black finish is blackened and polished, not a coating that chips, but it wears to an antique look over time.

Responsible use

A prong collar is a training tool, not an everyday collar. Use it only on a lead, during training, with guidance from an experienced trainer. Sprenger says not to use it off lead or for travel, and in our trainers' view it should never be left on an unsupervised dog.

Sprenger does not recommend prong collars for dogs under about 7–9 months. The law also differs across the UK: Wales's dog welfare code calls prong collars "not acceptable", and Northern Ireland is considering a ban. Read are prong collars legal in the UK? before you buy.

Shop the kit

Related guides: how to fit a fur saver collar and grot collars and slip leads. See all dog training collars.

FAQs

What size prong collar does my dog need?

Choose the gauge by weight first: 2.25 mm for dogs up to 18 kg (40 lb), 3.2 mm for dogs up to about 40 kg. For dogs over about 40 kg, ask us for advice. Then measure behind the ears and adjust the length with links.

How tight should a prong collar be?

As a trainer guide: snug enough to stay high behind the ears without sliding down, with room to slide one finger under the chain. If it slips down the neck when your dog moves, remove a link.

Can I add links from a different size collar?

No. Links must match the wire gauge. Use 2.25 mm links on a 2.25 mm collar and 3.2 mm links on a 3.2 mm collar.

Is a ClicLock collar safer than a standard one?

It is quicker and easier to put on and take off, and its slider stops the button opening by accident. Fit is still set by the links, so size it the same way.

Should my dog wear a prong collar all day?

No. Put it on for training and take it off afterwards. Use a flat collar for ID tags.

Need help with sizing?

Browse our prong collars and the full Herm Sprenger range. If you're unsure which gauge or how many links, email info@k9store.co.uk with your dog's weight, breed and neck measurement, and one of our trainers will help.