Pneumatics|Automation|Published Nov 5, 2026|12 MIN READ
Which Seal Kit Fits My SMC Cylinder? A Model-Number Checklist for NCA1/NC1A and MGP
Start with the full model number on the label, including every suffix. Confirm the series and bore, find SMC’s parts list for that exact series, then check whether the cylinder is serviceable and which seals the kit contains. If the label is incomplete or a suffix is unfamiliar, send photos to technical support before ordering.
Three recent live chats asked the same question in three different ways. Each answer starts in the same place: the model number on the label.
Which Seal Kit Fits This Tie-Rod Cylinder?
What Is the Kit Reference for This Number?
Do Repair Kits Exist for This Compact Guide Cylinder?
1. Record the Full Model Number and Every Suffix
Copy the model number from the cylinder’s label exactly, including the dashes and everything after the stroke, and take a photo of the label. Purchase records and memory are useful backups, but cylinders get swapped, modified and relabelled over the years.
The suffix is the easiest part to miss, and it can change which seals fit.
Rule of Thumb
If you can’t read the whole model number, you can’t pick the kit. A clear label photo is the fastest fix.
2. Confirm the Series
The first letters identify the product family. Seal kits are designed for one series, so never assume a kit from one family fits another, even at a similar bore.
Tie-Rod Cylinder
- NFPA-Style Tie-Rod Construction
- Bore and Stroke Codes in Inches
- Seal Kits Listed in the Series Catalog
- Standard Kits Exclude Several Options
Compact Guide Cylinder
- Slide Bearing (M) or Ball Bushing (L, A) Versions
- Bore and Stroke in Millimetres
- Seal Kit Search on SMC’s Maintenance Site
- One MGP-Z Kit per Bore
Watch Out for Part Numbers
SMC uses the NC1A prefix on NCA1 component parts, such as seal kits and cylinder tubes. A number like NC1A250-0300-XA39MB5 does not follow the standard NCA1 ordering format and carries a special suffix, so it needs a factory lookup rather than a catalog search.
3. Confirm the Bore and Units
Seal kits are ordered by bore, so read it carefully and note the units. In NCA1 model numbers, the bore code is in inches and the stroke is in inches and hundredths: NCA1B400-1200 has a 4 in bore and a 12.00 in stroke. MGP model numbers use millimetres: MGPL25-125Z is a 25 mm bore, 125 mm stroke cylinder with ball bushing bearings.
4. Find the OEM Parts List for That Series
SMC publishes replacement parts information by series. Its maintenance site includes a seal kit search for many cylinder families, including the MGP. For series that are not listed there, such as the NCA1, SMC points to the replacement parts list in the series catalog.
5. Check Whether Options Change the Kit
Standard kits are written for standard cylinders. SMC’s NCA1 catalog says its seal kits are for standard single rod, double acting cylinders without options, and that they do not apply to the following:
Kits for these options are confirmed through SMC.
6. Decide Whether the Cylinder Is Worth Resealing
Before ordering, check where the air is leaking and inspect the rod and bore surfaces. If they are damaged, compare the cost and downtime of a repair with a new cylinder.
A Seal Kit Replaces
- Piston and Rod Seals
- Gaskets
- Cushion Seals, Where Fitted
A Seal Kit Won’t Fix
- A Scored or Bent Piston Rod
- A Worn or Damaged Cylinder Tube
- Worn Guide Bearings
7. Send the Right Details When the Label Is Incomplete
If the label is worn, painted over or missing, or the model number does not match the series format, contact technical support before ordering anything. A few clear photos usually settle the question faster than a description.
Label Close-Up
Every Character Readable
Whole Cylinder
Shows Series and Size
Mounting
Brackets and Bolt Pattern
Rod End
Thread and Attachments
Add the measured bore and stroke if the label is missing.
What the Three Requests Tell Us
| Model Number | Series | Bore and Stroke | Next Step |
|---|---|---|---|
| NCA1B400-1200 | NCA1 Tie-Rod, Basic Mount | 4 in Bore, 12.00 in Stroke | Use the NCA1 Parts List |
| NC1A250-0300-XA39MB5 | Not Confirmed | Not Confirmed | Send Label Photos |
| MGPL25-125Z | MGP-Z Compact Guide, Ball Bushing | 25 mm Bore, 125 mm Stroke | Use the MGP-Z Parts List |
Seal Kit Basics
Model Number First
The full label number, including every suffix, decides the kit.
Series
NCA1 and MGP use different kits and parts lists.
Bore
Kits are ordered by bore. Check whether it is in inches or millimetres.
Options
Suffixes such as double rod or Viton seals can need a different kit.
Grease
The MGP-Z kit does not include grease. Order the grease pack separately.
Serviceability
A kit replaces seals and gaskets, not a worn rod, tube or bearing.
Sources: SMC MGP-Z maintenance parts list and SMC NCA1 series catalog.
Checklist: What to Send Proax Before Ordering a Seal Kit
A Seal Kit Request Goes Faster With This Information:
Not Sure Which Kit Fits?
Send your model number and label photos, and our in-house team will help you find the right kit or the right next step.
