What is the difference between OF and OFHD seals?

So even though strapping has been around for quite some time, we always see clients using the incorrect seals on their strapping, most of the time though its not their fault, most packaging companies have absolutely so idea when it comes to plastic strapping and seals as people buy them through resellers where strapping isn't their main product. Its ours, we want you to use the right seal for the right job. 

A common problem we see if often customers will buy 19mm heavy duty black plastic strapping then use them with standard grade OF seals. Now at some point they were probably using OFHD seals, but some information got lost away and a buyer was only looking at the price and look of the seal and not its gauge. 

So what happens is a client buys heavy duty 400kg breaking strain strap, then use a standard grade, OF seal. while it will work and it will hold, it wont hold to the force of a HD seal, so you're simply wasting money on buying the 400kg strap or you're creating a dangerous situation where your seal wont hold to the expected break strength. 

Maybe one day we'll dust off our break testing machine and write up a more detailed comparison on seal strength. BUT TODAY IS NOT THAT DAY. 

Understanding the Difference Between OF and OFHD Plastic Strapping Seals

When you’re working with polypropylene (PP)  strapping the seal you choose is just as important as the strapping itself. At MPS Packaging Australia, we supply both OF (Open Flange) seals and OFHD (Open Flange Heavy Duty) seals, and each type is designed for a different level of load security. Understanding when to use each one ensures your strap joint is strong, consistent, and reliable in transport.

What Are OF Plastic Strapping Seals?

OF seals are the standard open-flange seals used with everyday PP plastic strapping. They’re engineered for general-purpose applications where the load is moderate and the strapping is not tensioned to extreme levels.

These seals are ideal for common packaging tasks such as bundling cartons, securing warehouse goods, strapping lighter pallets, and day-to-day warehouse operations. They crimp down firmly and provide an economical, tidy closure that matches the performance of standard PP strapping perfectly.

OF seals should be used with "standard grade" strapping such as hand strapping or machine grade strapping, this strapping is commonly, blue, yellow or white/clear. 

What Are OFHD Plastic Strapping Seals?

OFHD seals, or Open Flange Heavy Duty seals, are designed for applications where the strapping is under higher tension or the load is heavier. These are typically used with heavy-duty black plastic strapping

While they look similar to standard OF seals, their heavier gauge makes them far better suited for demanding environments — heavy products, rough handling, long-haul transport, steel components, timber, and situations where you simply need a stronger, more secure joint. They still work with the same style of manual sealer, but they deliver a stronger bite and higher retention on the strap.

What sealer should is use with OF or OFHD Seals?

The sealer required for a use on OF and HD seals are the same, they are plastic strapping sealers with teeth. OF and OD seals are"shred-able" seals. when the strap is sealed you should see clear teeth marks in the top of the strap. 

ITS IMPORTANT TO NOT USE A STEEL STRAPPING SEALER OR PET STRAPPING SEALER FOR THE FOLLOWING REASONS:

Steel strapping seals crimp the edge of the seal/strap, they're designed to bend steel strap in and lock it into place, plastic strap is not ridged like steel so the plastic strap and easily slide through in this method. 

PET strapping seals have seated teeth in them, they may look like OF seals from a distance as the profile is similar, however PET strapping seals have teeth inside them designed to dig into the strapping. PET strapping Sealers dont have teeth, they're flat internally and designed to press the gripper seal closed and not "shred" the seal and strap. 

Summery. 

Choosing the right seal might seem like a small detail in your strapping process, but it’s one of the biggest factors in whether your load stays secure, performs to its rated strength, and remains safe during handling and transport. At MPS Packaging Australia(Formerlly Melbourne Packaging Supplies, we’ve seen firsthand how the wrong seal can undermine even the strongest strap — turning a 400 kg rated product into something performing closer to half its capability. That’s wasted money, unnecessary risk, and a preventable cause of load failure.

By understanding the difference between OF and OFHD seals, and matching them correctly to standard or heavy-duty PP strapping, you ensure every joint is as reliable as the strap itself. OF seals are perfect for everyday warehouse applications, while OFHD seals are built for high-tension, heavy-weight, and industrial loads. Pairing the right seal with the correct manual sealer ensures proper bite, proper grip, and proper performance.

Our goal at MPSPACK isn’t just to sell strapping and hardware — it’s to make sure our customers get the safest, strongest, and most cost-effective results possible. If you’re unsure which seal, strap, or tool you need, we’re always here to help. When your strapping is matched properly, your loads are more secure, your workflow is safer, and your packaging performs exactly the way it should.