The 1670.7/4 sits between the bare-socket 1670.5/4 and the integrated-handle 1670.8/2BI-US in the Unior cassette-lockring lineup. It's the same Shimano/SRAM HG 12-spline socket as the basic tool, with one critical addition: a centering guide pin that anchors the tool against the wheel's quick-release skewer. The handle stays separate; you bring your own ratchet or breaker bar to the back. The guide pin is what stops the tool from popping out of the lockring splines under load. On a stuck lockring, the splines take all of the load through a small contact patch; without a pin holding the socket centered, the first hard pull tilts the tool, the splines pop, and the lockring rounds. The guide pin slides through the lockring's central bore and through the wheel's QR skewer, holding the splines in full engagement through the break-free. The choice between the 1670.7/4 and the basic 1670.5/4 is whether you've got a particularly stuck lockring or a freshly-installed one. For shop bikes serviced annually, the splines stay clean and the 1670.5/4 works fine. For wheels coming in for the first cassette change after years of weather, the guide pin is the difference between getting the lockring off and rounding the splines. How to use it Thread the wheel's QR skewer out, slide the 1670.7/4's guide pin into the lockring bore, and re-thread the skewer through the tool and back into the hub. Snug the QR against the back face of the tool. Hold the cassette still with a chain whip or Cassette Wrench, then turn the 24 mm wrench flat or 1/2" drive counter-clockwise. Loosen the QR a quarter turn each time the lockring breaks free further; the tool can lift back out as the lockring threads out. For thru-axle hubs the guide-pin spec is different; the 1670.7/4 expects a QR-style skewer bore, while thru-axle hubs need the 12mm Guide 1670.9/4 instead. Compatibility Shimano HG cassettes, 7- through 12-speed SRAM HG cassettes (XD and XDR included; HG lockring pattern) Microshift and Sunrace cassettes using the Shimano HG lockring pattern QR-skewered hubs only; not for 12 mm thru-axle (use 1670.9/4) Not for Campagnolo (use 1670.4/4) Specs 12-spline Shimano/SRAM HG lockring pattern Centering guide pin for QR-skewered hubs 24 mm hex wrench flat 1/2" square drive socket on the opposite face Trivalent chrome plated to ISO 1456:2009 Article number: 1670.7/4 Built in Zreče, Slovenia Unior has been forging hand tools in Zreče since 1919, and sponsors professional road and mountain-bike race teams. The 1670.7/4 is the middle tool in a three-step lineup, and the design call is deliberate: workshops doing cassette work daily get the integrated-handle 1670.8/2BI-US, workshops doing it monthly get the 1670.7/4 with their existing ratchet, and the bench tool 1670.5/4 covers the once-a-season service for clean lockrings. Pro tip from our mechanics The guide-pin trick; snugging the QR against the tool's back face; does the same work as our integrated-handle version's anchor. The 1670.7/4 just gives you the choice of which ratchet to use; if your ratchet has a longer arm than our integrated handle, you'll out-leverage the integrated tool. Most workshops have a 250 mm or longer 1/2" breaker bar in the drawer already. The cassette-replacement workflow covers when the leverage difference matters and when it doesn't: When and how to replace your cassette → FAQ What is a cassette lockring tool used for? It engages the splined lockring that holds a cassette in place so the lockring can be turned out counter-clockwise. The 1670.7/4 is the Shimano/SRAM HG version: a 12-spline socket driven by a 24 mm wrench or 1/2-inch ratchet, with a cassette wrench or chain whip holding the cassette still. Why does the 1670.7/4 have a guide pin? Spline engagement on a cassette lockring is shallow, and a seized one takes real force to crack; an unanchored socket tends to cam out at exactly that moment and chews up the lockring. The pin passes through the lockring bore, the skewer threads back through the pin, and the clamped-down assembly keeps the splines mated until the lockring gives. Which other tools do I need alongside the 1670.7/4? The handle is bring-your-own: drive it from the 1/2-inch square socket with your ratchet or breaker bar, or put a 24 mm wrench across the hex flat. Add a cassette wrench or chain whip to hold the cassette, and the wheel's own quick-release skewer, which anchors the guide pin. Can the 1670.7/4 be used on 12 mm thru-axle hubs? No; the guide pin expects a quick-release skewer bore. Thru-axle hubs take the 1670.9/4, which pairs the same HG socket with a 12 mm guide.
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