Square Profile Nipple Driver

The square-profile internal spoke nipple is the workshop-friendly alternative to slot-head and Torx nipples. The square recess is shallow enough to engage cleanly even when the nipple is slightly recessed in the rim's spoke hole, and the four-corner contact distributes torque without the round-out risk that a slot-head can present under high build torque.

The 1751/2Q is the dedicated driver for the 3.2 mm square-profile internal nipple; a common size on aero and deep-section rims, where the internal nipple geometry needs to clear the spoke hole and seat well into the rim's spoke bed. The driver's 80 mm shank reaches through standard double-wall and most deep-section aero rims; the 6.5 mm outer diameter of the shank clears most spoke holes without binding.

A knurled handle gives the grip its working comfort, particularly when spoke tension is high and the nipple is harder to turn against the spoke's pull. Build sessions on deep-section aero wheels with square nipples are where this tool earns its space on the bench.

Compatibility

• Nipples: 3.2 mm square-profile internal spoke nipples.
• Rims: standard double-wall and most deep-section aero (up to about 60 mm depth).
• Wheels: aero road wheels with internal-nipple builds; most modern deep-section wheelsets that use square-profile nipples.

Specs

• Engagement: 3.2 mm square tip.
• Shank length: 80 mm (clears most deep-section aero rims).
• Shank diameter: 6.5 mm outer diameter (clears most spoke holes).
• Handle: knurled grip for workshop comfort under high spoke tension.

Built in Zreče, Slovenia

Unior has been forging hand tools in Zreče since 1919, and sponsors professional road and mountain-bike race teams. The square-profile nipple is one of the smarter manufacturing decisions in modern wheelbuilding; easier to engage cleanly, harder to round out, friendlier to the workshop. The 1751/2Q is the driver that pairs with that nipple geometry; a generic flathead screwdriver will engage briefly and then strip the recess, and a slotted driver will not engage at all.

Pro tip from our mechanics

When the nipple recess is recessed below the rim's outer face (common on internally-spoked aero wheels), the 80 mm shank length of the 1751/2Q is the difference between a clean engagement and a half-engagement that strips the recess. If a shorter driver makes contact but won't fully seat, the engagement is partial and the round-out is one or two turns away. Reach for the 1751/2Q or the Speed Nipple Bit 2.5mm before applying torque. The full wheel-building workflow is in How to true a bike wheel →