Key Takeaways
What it is. A metric cable gland designed to let a cable pass through an enclosure while sealing against dust and water.
How it works. Tightening the cap compresses an internal elastomer ring that grips the cable jacket and creates the environmental seal.
About the white piece. On many models a white insert serves as a reducer for smaller cables; removing it allows larger diameters. The black elastomer ring remains in place for sealing.
Final ID. The clearly molded text “SYNTEC” and “M25×1.5” confirm a polyamide (nylon) metric gland sized for mid-diameter cables, with exact clamping range depending on the specific model.
Story & Details
A close look at the hardware. The assembly consists of a threaded body with a hex collar, a dome cap with grip texture, a compressible elastomer ring, and—in some variants—an additional white insert. The thread is male and intended to pass through a punched or tapped entry, typically secured with a locknut if the wall is not threaded.
Mechanics of the seal. Feed the cable through the cap into the body. As the cap tightens, it drives the elastomer ring radially inward. That action both seals the opening (the ingress-protection function) and provides strain relief so the cable can’t be tugged out easily.
What the white insert does—and doesn’t do. Where provided, the white insert is a diameter reducer for small cables. Removing it widens the usable range without compromising the seal, because the black elastomer ring is the component that actually seals. A superficial line on a plastic insert may be only a molding trace; if it doesn’t flex open with gentle pressure, treat it as non-functional and do not cut it. If the cable still doesn’t fit after removing a reducer, step up one gland size rather than modifying the seal.
Reading the markings. The molded “M25×1.5” specifies a 25 mm metric thread with a 1.5 mm pitch. That places the gland in a size class where many manufacturers list clamping ranges roughly in the high single digits to the mid-teens of millimeters—always check the data sheet for the exact variant.
Standards frame the choices. Selection and testing practices trace back to International Electrotechnical Commission standards. IEC 60529 defines ingress-protection codes. IEC 62444 focuses on construction and performance of cable glands themselves. Together they explain why the elastomer seal and correct sizing matter more than cosmetic parts.
Conclusions
The verdict. It is a polyamide metric cable gland clearly identified as M25×1.5.
The practice. Route the cable through the cap and body, tighten until the elastomer ring grips firmly, remove any reducer only when a larger cable is required, and verify the cable’s jacket diameter against the model’s clamping range. When in doubt, move to the next size rather than altering the seal.
Sources
IEC — Ingress Protection (IP) ratings overview: https://www.iec.ch/ip-ratings
IEC — IEC 62444 standard page (cable glands): https://webstore.iec.ch/en/publication/7034
LAPP — SKINTOP ST-M product page with clamping ranges and IP ratings: https://products.lappgroup.com/online-catalogue/cable-glands/skintop-cable-glands-plastic-metric/standard/skintop-st-m.html
LAPP (regional listing) — ST-M 25×1.5 variant with 8–17 mm clamping range: https://e.lapp.com/in/p/plastic-cable-glands/skintop-st-m-25×1-5-ral-7035-lgy-53111430
Phoenix Contact — Cable-gland families and thread options: https://www.phoenixcontact.com/en-pc/products/cable-entry-system-and-cable-glands
YouTube (institutional) — LAPP Group, short product overview explaining cable-gland function: https://www.youtube.com/watch?v=kpFgkBqOZqA
Appendix
Cable gland. A mechanical fitting that allows a cable to pass through an enclosure while providing strain relief and a barrier against dust and liquids.
Dome cap. The outer knurled cap that, when tightened, compresses internal components to clamp and seal around the cable jacket.
Elastomer seal. The compressible ring inside the gland that provides the true environmental seal and much of the strain relief when the cap is tightened.
IP code. The ingress-protection classification, defined by IEC 60529, that rates resistance to dust and water for enclosures and accessories.
Locknut. A nut used on the inside of a panel or enclosure to secure a gland’s threaded body when the entry hole is not tapped.
M25×1.5. A metric thread specification with a 25 mm major diameter and a 1.5 mm pitch, common for medium cable diameters.
Mold mark. A superficial line or dot left by the injection-molding process; it has no functional role and should not be pried open or cut.
Reducer (insert). An optional plastic sleeve that adapts the seal for smaller cable diameters; removing it expands the usable range while the elastomer ring continues to seal.
Strain relief. The protective function that limits cable movement and pull-out forces at the entry point to safeguard connections inside the enclosure.
Threaded body. The main gland section with external threads that passes through the enclosure wall and interfaces with a locknut or tapped entry.
My Diary - Leonardo Cardillo 