The TP-218 piston profile
These piston T seals are the TP-218 reference, associated with the AS568-218 size. The exact listing specifies a 70-durometer Buna, or nitrile, sealing body with nylon backup rings. The construction and piston profile are part of the product identity; this is not simply an ordinary O-ring sold under another name.
The listed cross section is 0.125 inch, inside diameter is 1.250 inches and height is 0.185 inch. Recorded metric equivalents are 3.18 mm, 31.75 mm and 4.70 mm respectively. Keep the height separate from cross section when checking the part, because the two values are different.
What the backup rings do
The source's family guide describes a T-shaped elastomer body supported by harder backup rings. Their purpose includes resisting extrusion and helping stabilize the seal in motion. For this exact TP-218 reference, the listing identifies the backup material as nylon. A different backup construction should not be assumed from a photograph or a general family description.
The TP profile is described as the outward-facing piston configuration for pressure in either direction. The rod profile is a separate type. This distinction matters when a parts list describes only a T-seal without giving the full reference. Identify whether the original component is a piston or rod seal before comparing nominal dimensions.
Compare T seals by profile and gland
The family guide discusses several base and profile arrangements. That information is useful for identifying what must be checked, but it does not establish that every T-shaped seal fits every O-ring groove. Compare the equipment's gland drawing with the exact TP-218 specification rather than assuming that the AS568 size alone guarantees a retrofit.
For a replacement review, keep the original part number, profile and complete dimensions together. If an old seal has changed shape in service, use the equipment drawing or original part reference to resolve the intended size. Do not change the request to a nearby size on the basis of a worn part's appearance.
Material and operating conditions
The researched TP-218 uses the specified nitrile body and nylon backups. The material identity is not a blanket compatibility statement for every fluid or temperature. Operating pressure, motion, temperature and the actual fluid all belong in an application assessment before a purchase.
The general T-seal guide includes family operating information. We do not present that as a separately validated rating for your cylinder or convert it into a performance guarantee. The component, gland and working conditions need to be considered together by the person responsible for the equipment.
Read dimensions independently of the illustration
The product illustration helps show the relationship between the seal and its backup elements. It is not a dimensional drawing, and the apparent spacing or thickness in an image should not be used to calculate fit. Use the recorded specification and source documentation for dimensional comparison.
Cross section, inside diameter and axial height describe different aspects of the reference. For example, the 0.185-inch height should not be replaced by the 0.125-inch cross section simply because both are small dimensions in the same listing. A careful check keeps these values attached to their original labels.
What is included in the request
One proposed request unit represents one TP-218 piston T-seal product with the listed nylon backups. It does not represent a complete cylinder repair kit, piston assembly, rod wiper or guide ring. Related components must have their own exact references and verified relationships.
This page is restricted to TP-218. Other sizes, rod styles and locking-profile versions are not selectable substitutes in the availability form. Keeping the exact SKU intact helps avoid a later discussion about a product that merely resembles the one originally requested.
Requesting T seals from Plethara
Enter the number of TP-218 units you want checked, along with your name and email. The review screen lets you confirm the exact product and quantity before submitting interest. Selecting a quantity does not reserve inventory, fix a price or authorize work on an order.
The final confirmation is an interest request only. We will confirm availability, final price and delivery timing before any purchase. No card details are requested, no payment is collected and no charge or fulfillment is authorized. The same exact product reference remains attached to the request for that follow-up.
Questions about TP-218
- Are these T seals the rod version?
- No. TP-218 is the researched piston profile. A rod seal would need its own verified reference.
- What are the seal and backup materials?
- The exact listing specifies a 70-durometer nitrile body with nylon backup rings.
- Is the axial height the same as the cross section?
- No. Height is listed as 0.185 inch; cross section is 0.125 inch.
- Does AS568-218 establish a universal O-ring replacement?
- No. Check the exact profile, base arrangement and gland drawing. A matching size reference alone does not establish interchangeability.