Collection: Stemming Plugs

Stemming plugs do one job: hold stemming material in place so your blast energy goes into the rock, not up the hole. If you're losing energy to blowouts, getting inconsistent fragmentation, or burning through stemming material because it won't stay put — the plug is the fix.

MTI's range of stemming plugs are built for drill and blast operations. Sized from 2 inches (50mm) through to 12 inches (300mm), they fit standard production holes across hard rock mining, quarry, and construction blasting.

How Stemming Plugs Work

A stemming plug sits inside the blast hole at a set depth above the explosive charge. It creates a physical barrier that holds the stemming column (usually drill cuttings or aggregate) in place.

When the charge detonates, the plug limits the blast energy from venting straight up the hole. That means more energy goes into breaking rock, and less gets wasted as noise, dust, and flyrock.

They can also be used to create air decks — a gap between the charge and the stemming that changes how the blast energy distributes through the rock mass. Air decking with a stemming plug can give you a consistent deck length, which you can't guarantee with alternative methods.

Stemming Plugs - product information

Which Stemming Plug is Right for You?

Mechanical plugs used to retain charge, block off holes, protect downlines, and manage voids across open-pit, underground, and tunnelling operations. Each plug in this collection uses a different mechanism — inflation, friction fins, collet-style retention, or spring-loaded shape — so crews can match the plug to the hole condition, diameter, and application instead of forcing one product to do every job.

BLASTBALL™

Air-Inflated Plug 

The only BLASTBAG™ with zero metal and zero hazardous materials. Purpose-built for sites requiring non-DG compliance and metal detector compatibility. Fits hole sizes between 3"-9". Most popular BLASTBAG™ used for underground blasting.

  • Widest size range in the collection: 2.5" – 10 5/8" (64 – 270 mm) 
  • Seals in wet holes, breakthroughs, cracks and voids 
  • Rated from -58°F to 185°F (-50°C to 85°C) 
  • Inflates with any standard air source such as a compressor or mine air (max 12 PSI) 

ROCKRIVETS™

Collet-Fin Retention Plug 

A hard-push plug that grips the hole wall with plastic fins that close like a collet. Engineered with dedicated slots so a downline or firing line passes through safely — reducing the chance of cut-offs and misfires.

  • Broad size range: 3" – 9" (76 – 230 mm) 
  • Rigid (hard plastic) for maximum holding capacity on larger loads and in warmer climates 
  • Semi-Rigid (soft plastic) for faster, easier installation, or colder climates 
  • Installs using a ROCKRIVET™ Connector that can be attached to an ANFO/Emulsion hose or a load pole. Once in place, a simple twist and the ROCKRIVET breaks free, leaving it securely in the hole. 

MiTiPLUG™ 

Fin-Style Uphole Plug 

A semi-rigid polymer plug built specifically for upholes. Flexible fins fold back during push-in, then grip the wall to hold emulsion or ANFO from slumping. The fin geometry lets emulsion gas through the plug while maintaining collar height.

  • Purpose-built for upholes in underground production 
  • Resistant to the chemistry in emulsions and ANFO 
  • Small-diameter range: 2.5" – 3.5" (64 – 89 mm) 
  • High pack count — 250 per box for high-volume loading crews 

SPRINGLOCK™

Tunnel Spider

A rigid plastic cartridge restraint built for tunneling. The spring-like shape slides in easily and locks against the hole wall, keeping the charge seated at the toe of the hole — which matters most on angled or upward holes where gravity wants to pull the cartridge back out.

  • Purpose-built for tunnelling and civil blasting 
  • Keeps cartridges at the toe of angled holes for better fragmentation 
  • Small-diameter: ~1.75" – 2" (45 – 50 mm) 
  • Highest pack count in the collection — 1,500 per box 

Detailed Comparison

FeatureBLASTBALL™ROCKRIVETS™MiTiPLUG™ SPRINGLOCK™
Plug TypeAir-inflated rubber bladderCollet-fin retentionSemi-rigid fin plugRigid plastic tunnel spider 
Primary Use Sealing, cracks/voids, breakthrough management, and liner deployment Charge retention with downline protectionUphole emulsion/ANFO retentionCartridge retention in tunnelling 
Hole Size Range2.5" – 10 5/8" (64 – 270 mm) 3" – 9" (76 – 230 mm) 2.5" – 3.5" (64 – 89 mm)~1.75" – 2" (45 – 50 mm)
Installation Air-inflated on drop line or charge hosePush-installed via ANFO hose or load pole using ROCKRIVET Connector Push-installed via charge hose or applicator Push-installed via charge hose or applicator
Downline / Firing Line Protection N/A Dedicated pass-through slots Yes (revised design) N/A (tunnelling cartridge use)
Wet Hole Capable Yes — lowered through water then inflated ---
Gas-Through Emulsion/ANFO --Yes — fins allow gassing-
Temperature Range -58°F to 185°F (-50°C to 85°C) Standard Store away from UV Standard
Ideal EnvironmentUnderground & surface, incl. wet holes & voids Underground & open pit Underground upholesTunnelling / civil
Qty per Box20 – 50 (size-dependent)25 – 125 (size-dependent)2501,500

Which Stemming Plug Is Right for You? 

Every plug in this collection is engineered to support stemming, or explosives charge in the hole. Each one excels in different conditions — find the one that best fits your operation.

Specifications

Sizes and Compatibility

MTI stemming plugs cover hole diameters from 2 inches (50mm) to 12 inches (300mm). Check individual product pages for exact sizing, depth ratings, and material specs.

All plugs are designed for standard production blast holes. If you're not sure which size fits your operation, contact us directly — the team can match you to the right product based on your hole diameter and bench setup.

Stemming Plugs - specifications

Stemming Plugs

FAQ's - Stemming Plugs

How do stemming plugs improve overall blast performance?

Stemming plugs create a tight seal in the blasthole, helping explosives work more efficiently. They can, combined with stemming, improve energy retention in the borehole, reduce airblast, and reduce stemming ejection so crews get safer, more consistent blast outcomes.

Why are stemming plugs important for mining and quarry operations?

They help stabilize the stemming column, control gas release, and deliver more predictable fragmentation. This improves blast quality across open pit, underground, and quarry environments.

What are the key advantages of using stemming plugs?

  • Improve stemming retention/confinement
  • Reduce airblast
  • Support consistent fragmentation
  • Help stabilize stemming in variable geology
  • Increase safety across mining and quarry operations
  • Can be used to create air decks in smaller diameter holes

How do I choose the right stemming plug for my site?

Select a plug based on your borehole diameter, geology, and blasting objectives. This collection provides options suited for underground, open pit, construction blasting, and quarry operations — allowing your team to match the plug to your specific needs.

In open pit applications, ROCKRIVETS™ are typically used. In underground operations, ROCKRIVETS™ are typically used unless you don't need to support a lot of weight, then the MITIPLUG™ (Pilgrim Hat) can be used.

What blasting applications benefit the most from stemming plugs?

They are ideal for production blasting, perimeter control, presplit work, and general shot optimization. They help achieve cleaner benches, better wall control, and improved fragmentation.

Do these stemming plugs work in different ground conditions?

Yes. These stemming plugs perform reliably in hard rock, soft rock, and mixed geology. They maintain a secure seal so your blast pattern remains consistent even in challenging ground.

Which One Fits Your Operation?

Still not sure? Contact us however you'd like and we'll help you figure out which stemming plug best fits your application.