Category · Stemming Plugs

Collection: Stemming Plugs

When the stemming plug doesn't match the hole, the blast pays for it. Vented energy. Slumped charge. Flyrock. Wasted explosive.

No single blast hole plug works in every condition — so we run four. Air-inflated, friction-fin spider, one-way expansion, and gas-permeable bristle. Match the plug to your hole, your loading method, and your application instead of forcing one product to do every job.

Sized 45mm to 230mm (1¾" to 9") for production drill and blast across open-pit mining, underground, quarry, and tunneling.

Built for

Coal overburden blasting

Save up to 15% on explosives per hole.

Products 6

FITS HOLES 1¾" to 9"

Retention Designs 4

Stemming plugs — also called blast hole plugs, hole plugs, spider plugs, pilgrim hats, or red hats — do one job: hold the charge where you put it so the stemming stays in place and the energy goes into the rock instead of venting up the hole. If you're losing energy to blowouts, getting inconsistent fragmentation, dealing with flyrock at the boundary, or watching emulsion slump in your up-holes — a better stemming plug can help.

MTi GROUP's range of stemming plugs is built for production, trim, and pre-split blasting across quarry, open-pit mining, and underground operations. Sized from 1¾ inches (45mm) through to 9 inches (230mm), they fit standard drill and blast holes. Four retention designs — air-inflated bladder, friction-fin spider, one-way expansion, and gas-permeable bristle — let you match the plug to your hole condition, loading method, and bench setup.

How Do 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.

What Are the Benefits of Stemming Plugs?

The right stemming plug can help you cut powder factor without giving up fragmentation, reduce flyrock at the boundary, protect pit walls on trim and pre-split rows, and stop wasted emulsion or ANFO from slumping during loading. It also protects your shock tube or detonator wire on the way down the hole.

One MTi GROUP customer — a large iron ore operation in South America producing 90 million tonnes per year — installed ROCKRIVET™ plugs to improve stemming confinement and energy retention. The result: a 38% reduction in P80 fragment size, a 15% reduction in top-size material, and a 40–75% increase in crater size compared to blasts without them.

Side-by-side

Pick the right one.
Every time.

Detailed Comparison

	BLASTBALL™	ROCKRIVETS	MITIPLUG	SPRINGLOCK	SLUMPSTOPPA™
Plug Type	Air-inflated rubber bladder	Semi-rigid fin plug	Rigid plastic tunnel spider	Rigid plastic tunnel spider	Bottle-brush bristle retention
MATERIAL	Reinforced natural rubber + nylon webbing	Rigid or semi-rigid plastic	Semi-rigid polymer	Rigid plastic	Polymer bristles + stainless steel spine
PRIMARY USE	Sealing, cracks/voids, breakthrough management, and liner deployment	Charge retention with downline protection	Uphole emulsion / ANFO retention	Cartridge retention in tunnelling	Uphole emulsion retention; controls slumping during loading
HOLE SIZE RANGE	2.5" – 8" (64 – 203 mm)	3" – 9" (76 – 230 mm)	2.5" – 4" (64 – 102 mm)	~1.75" – 2" (45 – 50 mm)	2.5" – 4.5" (64 – 115 mm)
INSTALLATION	Air-inflated on drop line or charge hose	Push-installed via ANFO hose or load pole using ROCKRIVET Connector	Push-installed via charge hose or applicator	Push-installed via charge hose or applicator	Push-installed via charge hose or ROCKRIVET Connector
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	—	Yes — bristles allow gassing
AIR DECKING CAPABLE	Yes	Yes	Limited (uphole retention primary)	No	No
TEMPERATURE RANGE	-58°F to 185°F (-50°C to 85°C)	Standard	Store away from UV	Standard	Store away from UV
IDEAL ENVIRONMENT	Underground & surface, incl. wet holes & voids	Underground & open pit	Underground upholes	Tunnelling / civil	Underground emulsion upholes
QTY PER BOX	25 – 50 (size-dependent)	25 – 125 (size-dependent)	250	1,500	48

Swipe to see all columns →

When to pick each

BLASTBALL™

Pick BLASTBALL™ when you've got wet holes, breakthroughs, or cracks and voids that need a reliable seal across an irregular bore. Reinforced rubber bladder with nylon webbing, rated -58°F to 185°F (-50°C to 85°C). Lowered through water on a drop line, then inflated with compressed air. The only plug in the collection rated for wet-hole deployment. Fits 2.5"–8" (64–203 mm).

ROCKRIVETS

Pick ROCKRIVETS when you need maximum charge retention with downline pass-through — open-pit production, hard rock fragmentation, or wall control on trim and pre-split rows. Collet-style fins bite the hole wall and don't walk, twist, or shift. Rigid versions hold heavier loads; semi-rigid versions go in easier in tighter holes. Iron ore case study: 38% smaller P80 with ROCKRIVETS installed. Fits 3"–9" (76–230 mm).

MITIPLUG

Pick MITIPLUG™ when you need a structural plug for underground upholes that holds emulsion or ANFO and protects the downline. Flexible pilgrim-hat fins fold back on insertion, then lock in place — and the fins let the column gas through. Revised design with improved downline protection. The most popular plug for underground emulsion and ANFO upholes. Fits 2.5"–4" (64–102 mm).

SPRINGLOCK

Pick SPRINGLOCK when you're tunneling or running angled drilling and need to lock cartridge explosives at the toe of the hole. Rigid plastic with a one-way shape — goes in but doesn't come back out. Ships 1,500 to a box for high-volume tunnel and civil operations. The economical choice when you're shooting a lot of small-diameter holes. Fits 1.75"–2" (45–50 mm).

SLUMPSTOPPA™

Pick SLUMPSTOPPA™ when you're loading emulsion in underground upholes and slump is wasting product, ruining collar height, or making a mess on the bench. Polymer bristles with a stainless steel spine hold the column while letting emulsion gas through. Push-installed with a charge hose or the ROCKRIVET Connector. The dedicated emulsion-slump solution for underground upholes. Fits 2.5"–4.5" (64–115 mm).

About Stemming Plugs

Different holes need different plugs.

Mechanical plugs that hold the charge, seal voids, and stop slumping in upholes — the small piece of hardware that decides whether your energy goes into the rock or up the hole. Used by drill-and-blast crews across quarry, open-pit, underground, and tunneling operations to keep blasts consistent shot after shot.

Field results

38%

Reduction in P80

Iron ore mine, South America

18%

Lower Stemming Costs

Documented across improved-stemming programs

01

BUILT FOR EVERY HOLE

Five retention designs covering 1¾"–9" (45–230 mm) — wet or dry, downhole or uphole, tunneling or production. Match the plug to your conditions instead of forcing one product to do every job.

02

LESS WASTE, BETTER BREAK

When the stemming holds, blast energy stays in the rock. Documented at a 90M-tonne iron ore operation running ROCKRIVETS: 38% smaller P80 fragment size and 15% smaller top-size material compared to blasts without them.

03

STAYS WHERE YOU SET IT

Friction fins, expansion shapes, inflated bladders, gas-permeable bristles — each design grips the hole and holds the charge at depth. No walking, no slumping, no second guessing between loading and shot.

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.
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.
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.
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.

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