Short answer: It depends on the end of the Unity Manufacturing spotlight shaft. If the intermediate tube has a milled flat, you need the flat-shaft set: bushing U-8918-P3 (our listing says it replaces U-8384-P) with screw U-8385. If the tube is round with no flat, you need the round-shaft set: bushing U-1834 with screw U-1836.
Last updated: October 2026 · By SpotlightDepot Team, an authorized Unity Manufacturing dealer · Compiled from Unity instruction sheet 420-A Rev. C (2007), the Unity U-6701-0101 handle parts sheets A460-8380 Rev. B (2008) and A460-8686 (2014), and our product listings.
We stock both sets and the complete handle: the wedge bushing and screw for flat shafts, the wedge bushing and screw for round shafts, and the Unity U-6701-0101 replacement handle, which our listing says comes with both.
How do I tell a flat spotlight shaft from a round one?
Disconnect the lead wire from power first and keep it disconnected until the handle is back on (420-A step 23C; 4392 step 11a). Then take the handle off the shaft: Unity's sheet 420-A has you remove the wedge screw and the wedge, then slide the handle assembly off (420-A step 12). Look at the intermediate tube, the inner tube that sticks out past the outer tube. If one side is milled flat, it is a flat shaft. If it is round all the way around, it is a round shaft. The old wedge tells you too: a flat wedge has a flat face that meets the tube, and the other style has a curved surface.
When the handle goes back on, the intermediate tube must stick out at least 1 inch past the outer tube, or the wedge flat won't engage (420-A step 16; 4392 step 5g). Bring the grip to the parking position, about 9 o'clock on a left-hand spotlight or 3 o'clock on a right-hand one, with the handle-housing key against one side of the notch. Keep pressing the handle toward the shaft so the switch contact stays on the rod contact while you insert the wedge and wedge screw (420-A step 18).
Which wedge bushing set fits my shaft?
| Shaft | Wedge bushing | Wedge screw | Order |
|---|---|---|---|
| Flat (intermediate tube has a milled flat) | U-8918-P3; our listing says it replaces U-8384-P, the flat wedge bushing on the Unity handle sheets | U-8385 | Flat-shaft set |
| Round (no flat) | U-1834 (curved wedge bushing on the Unity handle sheets) | U-1836 | Round-shaft set |
Each set is one bushing and its matching screw. The U-8918-P3 part number and its replacement of U-8384-P come from our flat-shaft listing; the Unity handle sheets from 2008 and 2014 show the flat bushing as 8384-P (U-8384-P).
Can I use the round-shaft screw with the flat bushing?
No. Both Unity parts sheets for the U-6701-0101 handle say each screw fits only its own bushing. On the 2014 sheet (A460-8686), wedge screw U-8385 fits only the flat bushing U-8384-P, and screw U-1836 fits only the curved bushing U-1834. The 2008 sheet (A460-8380) gives the same pairing, with the same part numbers without the U- prefix (8385, 8384-P, 1836 and 1834). Order the matching set rather than a loose screw.
Does the flat wedge do anything besides lock the handle?
Yes. On a flat shaft, the flat on the wedge meets the flat on the intermediate tube when you install the handle, and that sets the head's parking position automatically (420-A step 15A, Fig. 12). On a round shaft there is no flat to line up, so you set the parking position by rotating the head toward the windshield, leaving at least 1 inch between the head and the vehicle, and tightening the up-down set screw (420-A step 15B).
Should I buy a wedge set or a whole handle?
If the handle works and only the wedge or screw is worn, damaged or lost, the wedge set is the cheaper fix. If the grip, toggle or switch is the problem, look at a complete handle. Several of our replacement handles come with wedge hardware, according to their product pages:
- U-6701-0101 (fits Unity spotlights marked M10000, S6, S04, 325-380, 260-280 or H1, among others) and 6701-0152 (1992–2011 Ford Crown Victoria Police Interceptor) include wedge bushings and screws for both flat and round shafts.
- U-6701-0290 (2011–2019 Ford Interceptor Utility / Explorer) includes the flat-shaft screw U-8385 and bushing U-8384-P.
The vehicle-specific factory replacements for the Tahoe, Charger, Impala, Interceptor Sedan and 2020 and later Interceptor Utility list hardware for flat shafts; U-6701-0102, 6701-0173, 6703-0104 and U-6701-0476 list no wedge hardware. See Genuine Unity Spotlight Replacement Parts for every handle we stock and what each one fits.
How tight should the wedge screw be?
The value depends on the wedge type and the Unity sheet for your installation, and the sheets disagree, so we keep every value in one place: Unity Spotlight Torque Specs: Every Screw in One Table. Use the sheet that came with your kit.
Frequently asked questions
What is the difference between U-8384-P and U-1834?
U-8384-P is Unity's flat wedge bushing, for spotlight shafts whose intermediate tube has a milled flat. U-1834 is the curved wedge bushing, for round shafts with no flat. Our flat-shaft set ships with bushing U-8918-P3, which our listing says replaces U-8384-P.
Which screw comes with the Unity flat wedge bushing?
Wedge screw U-8385. Unity's handle parts sheets say U-8385 fits only the flat bushing, and U-1836 fits only the curved bushing U-1834.
Does the Unity U-6701-0101 handle come with wedge bushings?
Yes. Our U-6701-0101 listing includes wedge bushings and screws for both flat and round shafts, so you can fit it to either shaft type on the spotlight series listed on its page.
How do I know if my spotlight shaft is flat or round?
Disconnect the lead wire from power first, then remove the wedge screw and wedge, slide the handle off and look at the intermediate tube. A milled flat on one side means a flat shaft; a fully round tube means a round shaft.
Next step
Order the flat-shaft set or the round-shaft set. Still not sure which shaft you have? Email a photo of the shaft end to info@spotlightdepot.com, or Ask a question with your spotlight model. Ordering for a fleet? Request a Quote.
