Royal Enfield Punjab Silencer DB Killer / Sound Reducer – HK Old Is Gold | 45mm, 57mm & 63mm

HK Old Is Gold DB Killer / Sound Reducer for Royal Enfield Punjab Silencers – 45mm, 57mm & 63mm

If your Royal Enfield Punjab silencer is too loud for everyday use, this HK Old Is Gold removable DB killer / exhaust baffle / silencer sound reducer is designed to reduce the exhaust outlet opening and moderate the exhaust note without replacing the complete silencer.

This listing brings the three commonly sold Punjab-silencer mouth sizes into one properly explained product:

• 45mm – Small Mouth
• 57mm – Big Mouth
• 63mm – Extra Big Mouth / newest largest size

Brand: HK Old Is Gold / HK
Product: Removable DB Killer / Sound Reducer / Exhaust Baffle for compatible Punjab-style silencers
Finish: Black
57mm HK box reference: HKDB2 – “DB KILLER PUN. (57MM)”

Important: Buy by the actual silencer mouth/outlet size, not simply by motorcycle model. A Classic 350, Bullet, Electra or Reborn can be fitted with different aftermarket silencers, so the motorcycle name alone does not determine whether you need 45mm, 57mm or 63mm.

Choose the Correct Size

45mm vs 57mm vs 63mm – What Does the Size Mean?

The 45mm / 57mm / 63mm measurement refers to the rear silencer mouth / outlet family for which the reducer is intended. It is not the motorcycle exhaust-header diameter, bend-pipe diameter or engine-port diameter.

This distinction matters because the same motorcycle can be running:

• a Small Mouth Punjab silencer,
• a Big Mouth Punjab silencer,
• a newer Extra Big Mouth 63mm silencer,
• or an entirely different exhaust design.

Therefore, never select the DB killer only because your motorcycle is called Classic 350, Bullet 350, Electra, Reborn or another Royal Enfield model.

How to Measure Before Ordering

1. Allow the exhaust to become completely cold.
2. Measure the inside opening / usable outlet diameter at the rear mouth of the silencer where the DB killer will sit.
3. Also check whether your silencer has the retaining-screw arrangement required for this style of removable insert.
4. Compare your measurement with the 45mm, 57mm and 63mm choices.
5. If your measurement is between sizes or the silencer has a different internal lip/step, do not force-fit the insert.

Best practice: if your existing silencer itself is sold as “45mm Small Mouth”, “57mm Big Mouth” or “63mm Extra Big Mouth”, choose the corresponding DB-killer size. If the exhaust brand/model is unknown, measure it physically.

Verified Market Size Mapping

Current Royal Enfield exhaust specialists sell Punjab-silencer DB killers in the same 45mm, 57mm and 63mm size families. The 45mm size is commonly associated with the Small Mouth format, approximately 56–57mm with Big Mouth, and 63mm with the newest Extra Big Mouth format.

The exact shape, internal step and retaining point can still differ between exhaust manufacturers, so matching diameter is necessary but should not be treated as the only possible fitment check.

What Does a DB Killer Actually Do?

A DB killer—also called a sound reducer, exhaust baffle, silencer insert, noise reducer or muffler insert—partially restricts the open outlet of an aftermarket exhaust. The purpose is to moderate an excessively loud exhaust note and make the bike more manageable for daily riding or longer journeys.

It does not turn an aftermarket exhaust into an original Royal Enfield silencer, and we do not publish a fixed “X dB reduction” because actual sound change depends on the complete exhaust system, silencer construction, engine, packing condition and installation.

Why Buy the Correct HK-Sized Reducer Instead of a Random Universal Insert?

• Three useful Punjab sizes: 45mm, 57mm and 63mm.
• HK Old Is Gold branding: intended for the Royal Enfield aftermarket exhaust market rather than an unidentified generic insert.
• Size-based selection: lets you match the reducer to the actual silencer mouth instead of guessing from the motorcycle model.
• Removable design: the insert is retained mechanically rather than permanently welded into the silencer.
• Black finish: visually unobtrusive inside the exhaust outlet.
• Replacement option: useful if the original removable reducer supplied with a compatible Punjab silencer has been lost or removed.

Compatibility – Read This Before Buying

This listing is primarily intended for Punjab / Long Punjab / Mini Punjab style Royal Enfield aftermarket silencers that use the matching mouth size and retaining arrangement.

Motorcycle Fitment – Why We Do Not List One Bike Model

A DB killer fits the silencer, not directly the engine or motorcycle chassis. A Royal Enfield Classic 350 UCE, Classic 350 Reborn, Bullet, Electra or other model may be using different aftermarket silencers with different outlet sizes.

For example, 63mm Long Punjab exhausts are currently sold in more than one Royal Enfield fitment configuration. The DB-killer decision should therefore be made from the installed silencer's outlet specification, not from the motorcycle name alone.

What You Receive

• 1 × HK Old Is Gold DB Killer / Sound Reducer in the selected size

The current 57mm unit shown is supplied as an HK-branded black removable insert with its retaining screw. Do not assume an Allen key or any additional tool is included unless it is physically present in the supplied HK package.

Installation Guidance

• Work only when the silencer is completely cold.
• Confirm size before insertion.
• Insert the DB killer squarely into the compatible exhaust mouth.
• Align the retaining point carefully.
• Tighten the retaining screw sufficiently to prevent movement, but do not overtighten and damage threads.
• Check that the insert cannot rotate, rattle or move outward.
• After the first ride, allow the exhaust to cool and re-check the retaining screw.
• If the insert needs excessive force, stop: the size or internal exhaust design is likely incorrect.

Sound & Performance – No False Promises

The purpose of this product is sound moderation. We do not claim a fixed decibel reduction, horsepower gain, mileage increase, throttle-response improvement or engine-performance benefit.

Installing a restrictive insert can change exhaust flow and sound characteristics. The result varies with the exhaust and motorcycle setup.

Road-Legal / Police-Challan Note

A DB killer does not automatically make an aftermarket silencer road-legal. Road legality can depend on the exhaust itself, applicable vehicle rules, approved noise limits and the actual sound produced by the motorcycle.

This item should therefore be purchased as a sound-reduction accessory, not as a guarantee against traffic enforcement, challans, inspection failure or noise-limit violations.

Frequently Asked Questions

Which DB killer should I buy for a Small Mouth Punjab silencer?

If the silencer outlet is the common 45mm Small Mouth format and the retaining arrangement matches, select 45mm.

Which size is for a Big Mouth Punjab silencer?

The established Big Mouth family is commonly around 56–57mm. Select the 57mm variant after measurement. The photographed HK 57mm package is marked HKDB2 – DB KILLER PUN. (57MM).

What is the 63mm version?

The 63mm option is the newest/largest mouth size in this three-size Punjab-silencer range and is intended for compatible 63mm Extra Big Mouth exhaust outlets.

Will 63mm fit every latest Royal Enfield?

No. The 63mm number describes the silencer outlet family, not the motorcycle generation. Your bike must actually be fitted with a compatible 63mm-mouth exhaust.

Will this fit my Classic 350 Reborn?

It depends entirely on the aftermarket silencer fitted to the motorcycle. If that silencer uses a compatible 45mm, 57mm or 63mm Punjab-style outlet and retention system, choose the matching size. Do not order only from the bike name.

Will this fit Bullet / Electra / Classic UCE?

The same principle applies: identify the aftermarket silencer and measure its mouth. The motorcycle model by itself is not enough to identify the correct DB-killer diameter.

Can I use it on a non-HK silencer?

Possibly, but only if the physical diameter, internal seating area and screw/retaining arrangement match. No blanket universal-fit claim is made for other exhaust brands.

Does the DB killer make the exhaust silent like stock?

Not necessarily. It is designed to reduce/moderate sound. The final exhaust note depends on the complete silencer and motorcycle setup.

How many dB will it reduce?

No verified fixed reduction figure is available for these HK inserts across every exhaust configuration, so we do not publish an invented decibel claim.

Does it improve mileage or power?

No mileage, horsepower or performance improvement is promised. This listing is for a sound-reduction insert.

Will fitting this stop police challans?

No guarantee can be made. The legality of an aftermarket exhaust depends on applicable regulations and the complete exhaust/noise setup. A DB killer can reduce sound but does not certify the exhaust as road legal.

What if I am not sure between 57mm and 63mm?

Measure the actual rear mouth/outlet of the silencer before ordering. Do not force the larger or smaller insert into the wrong exhaust.

Size Summary

45mm = Small Mouth
57mm = Big Mouth
63mm = Extra Big Mouth / newest largest option

For the lowest chance of a wrong order, measure first, then select the size.