The facts.
| Part number | G9988 |
|---|---|
| Type | Open, no perforation |
| Material | Stainless steel |
| Dimensions | Ø 45 mm, 100 mm long |
| Fitment | Universal |
| Road approval | None — track use only |
| Fits | Spark Grid-O silencers |
| Origin | Made in Italy |
| Manufacturer | Spark Exhaust Technology, Mantova |
| Manufacturer description | Grid-O - d.45 l.100 |
DescriptionThe whole story▼
Forty-five millimetres through a fifty-one and a half millimetre body. There is barely a wall left — which is exactly the point of this article.
Key Features
- dB killer for Spark Grid-O silencers.
- Ø 51.5 mm outer, 45 mm internal bore.
- Open type, no perforation.
- The widest and least restrictive of Spark's four Grid-O inserts.
- Stainless steel, removable.
- Spark part number G9988, made in Mantova, Italy.
Three Millimetres of Wall
Forty-five inside a fifty-one and a half body leaves about three millimetres all round. That is as little restriction as an insert can offer while still being an insert, and it is why this one costs a little more: a thin section in stainless takes more care to make than a thick one.
Who Needs the Widest One
Large-capacity machines, and venues whose limits are generous. On a big four or a large V-twin the narrower Grid-O inserts cost real mid-range, and if the machine only needs two or three decibels shaved off, the 45 does it without the penalty.
It is also the sensible first purchase if you do not yet know how far over the limit you are. Start wide, measure, go narrower if you must.
The Family Ladder
32, 38, 40, 45. Four bores, one body, one silencer family. Owners who run the same machine at different circuits sometimes carry two of the four; the swap takes minutes and needs a screwdriver.
Why All Four Are Open
Because the Grid-O ends in a woven titanium mesh across the whole outlet, and the mesh is already doing acoustic work. A perforated insert behind it would restrict without adding much attenuation, so Spark builds all four as plain bores.
The Price, and Why
The most expensive of the four Grid-O inserts, because it is the hardest to make. A three-millimetre wall in stainless has to be machined and finished without distorting, and there is less material to hold while that happens.
Ordering
One per silencer. If the case came to you without an insert, send us the exhaust's article number rather than guessing — the four look identical from outside and only the bore separates them.
Approval
Unaffected. A racing Grid-O stays a racing article with any insert fitted, and a homologated exhaust belongs in the configuration Spark tested it in.
FitmentWhich bikes this fits▼
Universal product — Please check whether it fits your bike.
Questions, one topic at a time.
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Our team is happy to help. Use the contact button below and we’ll personally help you choose the right gear or part.
Measure your head circumference about one centimetre above your eyebrows and compare it with the size chart on this page. Between sizes? Choose the smaller one — the padding beds in with use.
Yes — it’s tested and approved to the current ECE 22.06 standard and road-legal across the EU.
Most of our touring and sport helmets are Pinlock-ready and many include the insert. Check the ‘What’s in the box’ section on this page for this model.
Yes — the cheek pads are channelled so the arms of your glasses slide in comfortably.
Take out the washable lining and hand-wash it in lukewarm water. Clean the shell and visor with a soft cloth and water only — never solvents.
Our team will personally help you choose the right gear or part — around 24h for a reply.