Red Silicone Sealing Rings & Cord

What are red silicone sealing rings and cord?

Red silicone sealing rings and cord are O-rings and O-ring cord made from silicone rubber in a bright red colour. They have all the benefits of silicone, staying soft and flexible from deep cold to high heat, with the added advantage of being easy to see. The red colour makes them quick to identify, simple to check during maintenance, and easy to spot if a seal goes missing or breaks up.

Red silicone sealing rings and cord offer:

• A solid, round cross section, made in red silicone rubber (VMQ)
• Flexibility across a temperature range of around -55°C up to +225°C
• A hardness of 70 on the Shore A scale, the most common grade
• A bright colour that stands out against metal, plastic, and other seals.

The red colour is for identification.

• It does not change how the seal performs, but it makes it easy to tell red silicone seals apart from black nitrile, EPDM, or FKM seals in the same machine or stores.
• A bright seal is easier to see during inspection, and easier to find if part of it breaks away into a product or process.

Red silicone O-rings are referenced by section and bore, for example 4x24, and red silicone cord by its section diameter.

Why are red silicone sealing rings and cord essential?

In busy workshops and production lines, using the wrong seal material is a common cause of leaks and early failure. Colour coding helps prevent this. Using red silicone for silicone seals means fitters can see at a glance which material they are handling, and inspectors can quickly check the right seal has been fitted.

In food, drink, and hygienic environments, a brightly coloured seal is also easier to spot during cleaning and inspection. Red silicone combines this visibility with silicone’s wide temperature range and resistance to ozone and ageing, making it a practical choice for ovens, chillers, and processing equipment.

Typical applications include:

• Food and drink processing equipment, with certified material
• Bakery ovens, proving cabinets, and hot cupboards
• Chillers, refrigeration, and cold rooms
• Coffee machines and catering equipment
• Laboratory and pharmaceutical equipment
• Lighting and electrical enclosures
• Inspection hatches, lids, and access doors
• Any application where seals are colour coded by material

The main types of red silicone sealing rings and cord

• Red silicone O-rings - Ready-made red rings in set section sizes and bores, such as 1.6mm, 4mm, and 5mm sections. Ideal for standard grooves.
• Red silicone O-ring cord - Red silicone supplied as a continuous length and sold by the metre, for cutting and joining into custom-sized rings and seals.
• 70 Shore red silicone - The standard hardness, which gives a good balance of softness and sealing for most static applications.

How to choose the right red silicone sealing ring or cord?

• Colour coding - Choose red silicone where seals are colour coded, or where a visible seal makes inspection and cleaning easier.
• Temperature - Red silicone suits a wide temperature range, from around -55°C up to +225°C, so it suits hot and cold equipment.
• Static use - Like all silicone, red silicone is best for static seals. For seals that rub against moving parts, a tougher material may last longer.
• Fluid compatibility - Red silicone suits air, water, and many mild chemicals, but is not well suited to fuels and some oils.
• Food contact - For food-contact applications, make sure the red silicone is supplied with the correct food-grade certification.
• Size - Choose a section and bore to suit the groove, or a cord section and length to suit the seal size.

Essential references and specialised ranges

How the numbering works:

Red silicone O-rings are referenced by section diameter, then bore, in mm:

1.6x32.1 red silicone = 1.6mm section, 32.1mm bore

4x24 red silicone = 4mm section, 24mm bore

5x8 red silicone = 5mm section, 8mm bore

The outside diameter is the bore plus twice the section, so a 4x24 ring has a 32mm outside diameter.

Red silicone cord is referenced by its section diameter, for example 6mm red silicone cord. To work out the length of cord needed for a ring, add the bore to the section, then multiply by 3.14. For example, for a 60mm bore ring in 4mm cord: (60 + 4) x 3.14 = about 201mm of cord.

Suffixes:

RED or REDSIL = red silicone

VMQ = silicone rubber

70 = hardness on the Shore A scale

Suffix codes vary between manufacturers, so check the supplier’s catalogue for the exact meaning.

FAQ - All you need to know about red silicone sealing rings and cord

Is red silicone different from other silicone?

The material performs the same as other silicone of the same grade. The red colour is added to make the seal easy to identify and see. It does not change the temperature range or sealing properties.

Why choose a red seal?

Red seals are easy to spot during fitting, inspection, and cleaning, and help prevent the wrong seal material being used. In food and processing equipment, a brightly coloured seal is also easier to find if it becomes damaged.

Is red silicone food safe?

Red silicone is widely used in food equipment, but food-contact seals need certified material. Check the seal is supplied with the correct certification before using it in contact with food.

Can red silicone be used with oil or fuel?

It is not recommended. Fuels and some oils can make silicone swell and lose strength. For oil and fuel, use nitrile or FKM instead.

How do I fit a red silicone O-ring?

Make sure the groove is clean and free from sharp edges, as silicone tears more easily than many other rubbers. Ease the ring into place without stretching or twisting it. If lubrication is needed, use a product that is compatible with silicone.

How do I identify the size I need?

Measure the section diameter and bore of the old ring with callipers, or measure the groove it fits in. For cord, measure the section and work out the length needed from the groove size.

How can I tell if a red silicone seal needs replacing?

Warning signs include:

• Leaks around the seal
• A flattened ring that no longer springs back
• Tears, nicks, or splits in the rubber
• Faded, hardened, or swollen rubber
• Pieces of red rubber found in the product or equipment