Sylvania 21878 FBO31/835 T8 U-...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$22.45
Sylvania 21878 FBO31/835 T8 U-Tube Fluorescent Lamp, 31W, 3500K

Sylvania 21878 FBO31/835 T8 U-Tube Fluorescent Lamp, 31W, 3500K

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Model: 21878

In Stock (leaves warehouse same day if ordered before 3pm ET)

$22.45
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Sylvania 21878 FBO31/835 T8 U-Tube Fluorescent Lamp, 31W, 3500K

The Sylvania 21878 FBO31/835 is a T8 U-Tube fluorescent lamp built on Sylvania's Octron® Curvalume® platform, delivering a 31-Watt output with 2725 lumens and a warm-neutral 3500K color temperature. This U-bent lamp design uses a 2-Pin Medium Base and measures 22-1/2 inches in length, making it a compact-format replacement for troffer and recessed fixtures where a straight T8 tube will not fit. With an 82 CRI rating, the 21878 renders colors accurately for general commercial lighting applications, offering reliable, consistent illumination for facilities that rely on U-tube fluorescent fixtures.

Key Features

  • Lamp Type: T8 U-Tube fluorescent construction from the Octron® Curvalume® series, engineered as a compact bent-tube alternative to straight T8 lamps.
  • Wattage: 31-Watt lamp providing efficient light output for general-purpose commercial fixtures.
  • Light Output: 2725 lumens with a 3500K color temperature for a balanced, warm-neutral white light suited to offices, retail, and institutional spaces.
  • Color Rendering: 82 CRI delivers accurate, natural color rendering for tasks that require good visual clarity.
  • Base Type: 2-Pin Medium Base designed for compatibility with U-tube fluorescent sockets and fixtures.
  • Length: 22-1/2-inch overall length, sized for U-bend fixture cavities where standard 4-foot straight lamps cannot be installed.

Technical Specifications

  • Lamp Type: T8 U-Tube Fluorescent
  • Wattage: 31-Watt
  • Lumens: 2725
  • CRI: 82
  • Color Temperature: 3500K
  • Base: 2-Pin Medium Base
  • Length: 22-1/2 Inch
  • Series: Octron® Curvalume®

Typical Applications

  • Recessed Troffer and Compact Fixture Lighting
  • Commercial Office and Retail Lighting
  • Institutional and Educational Facility Lighting
  • Replacement Lamp for Existing U-Tube Fluorescent Fixtures
  • General-Purpose Interior Ambient Lighting

Why Sylvania?

Sylvania's Octron® Curvalume® U-tube fluorescent lamps are engineered to deliver dependable light output, accurate color rendering at 82 CRI, and a compact form factor suited to fixtures that can't accommodate a standard straight tube. The 21878 FBO31/835 combines a 31-Watt rating with 2725 lumens and 3500K color temperature, giving facility managers a consistent, code-compliant replacement lamp for commercial and institutional U-tube fixtures.

Manufacturer Resources

Product Specs

list_batch:
SYL-20260928
Product Type:
Fluorescent Tube
Product Wattage:
31W
Light Temperature:
3500K
Lumens:
2725
CRI:
82
Bulb Base:
2-Pin Medium Base
Series:
Octron Curvalume
Department:
Electrical
Product Group:
Lighting
Product Subgroup:
Lamps & Bulbs

Sylvania 21878 – Frequently Asked Questions

1) Will the Sylvania 21878 fit a 2x2 troffer that uses U-bent T8 lamps?
That is exactly what the 21878 FBO31/835 is for. It is a U-bent T8 fluorescent lamp with a 22-1/2 inch overall length and a 2-pin medium bi-pin base, so it drops into the U-tube sockets in 2x2 recessed troffers and other compact fixtures where a straight 4-foot T8 will not physically fit. Check that your fixture's lampholders are the medium bi-pin type before ordering.
2) Will a 3500K lamp match the 4100K tubes already in my building?
No. The 21878 is a 3500K lamp, a warm-neutral white, and it will read visibly warmer next to a 4100K cool white tube in the same room or the same fixture. If your standard is 4100K, order 4100K. For a cool-white linear T8 we carry the Philips Lighting 236794 in 4100K. Relamp a whole space or at least a whole fixture in one color temperature to avoid a patchwork look.
3) What exact lamp do I order to replace an FBO31/835 U-tube?
Order Sylvania part number 21878. The ordering code is FBO31/835, which reads as a bent-tube 31-watt lamp at 82 CRI and 3500K from the Octron Curvalume line. If the lamps you are pulling out are marked FBO31/835, this is the same lamp, same base, same output at 2725 lumens.
4) Can a Philips 236794 T8 lamp be used in place of the Sylvania 21878?
No. The Sylvania 21878 is a T8 U-Tube lamp with a U-bent body and a 2-pin medium base, sized at 22-1/2 inches so it drops into U-bend fixture cavities. The Philips 236794 is a linear T8 high output lamp rated 44 watts at 4100K, so it is a straight tube and will not seat in a socket pair spaced for a U-bend. Use the Philips linear lamp only where the fixture holds a straight T8 end to end.
5) What is the difference between a U-tube T8 lamp like the Sylvania 21878 and a straight 4-foot T8?
Same T8 diameter and same 2-pin medium base, but the 21878 is bent into a U so the whole lamp is 22-1/2 inches long instead of four feet. Both pins ends sit at one end of the fixture, which is why 2x2 troffers and shallow compact housings use them. A straight T8 cannot be substituted into a U-tube fixture, and vice versa, because the socket spacing and cavity length are different. At 31 watts it puts out 2725 lumens, so two of them in a 2x2 cover a similar area to a pair of 4-foot straight lamps.
6) Is the Sylvania 21878 a 31-watt lamp I can run on my existing T8 electronic ballast?
The 21878 is rated 31 watts and is a standard-output T8 lamp, which is the U-bend equivalent of a 32W 4-foot T8. It is designed for instant-start or program-start T8 ballasts of that type. It is not a high-output lamp, so do not pair it with an HO ballast circuit. Confirm your ballast label lists a U-bent or FBO31 lamp type.
7) My old U-tubes are marked FB32T8/835. Can I use the 31-watt Sylvania 21878 instead?
Mechanically yes in most cases, since both are T8 U-bent lamps on a 2-pin medium base, but the 21878 is a 31-watt lamp and a 32-watt lamp is a different wattage rating. Match the lamp type printed on your ballast label. If the ballast lists 31W U-bent T8 operation, the 21878 is the right lamp; if it only lists 32W, order the 32W version.
8) What is a higher color rendering alternative if 82 CRI is not good enough for a retail display?
The Sylvania 21878 renders at 82 CRI with a 3500K color temperature, which is the normal range for general commercial lighting. Where a space needs better color accuracy, the Philips 479634 Alto II is a high CRI linear fluorescent T8. It is a straight lamp, not a U-bend, so it suits a fixture that accepts a full-length linear T8 rather than the compact U-tube cavity the 21878 is built for.
9) I need more light out of the same fixture than the 21878 gives. What are my options?
The Sylvania 21878 is a 31-watt U-tube producing 2725 lumens at 3500K. For more output you have to move to a different lamp format: the Philips 236794 is a T8 high output linear lamp at 44 watts, 4100K, which also shifts the light cooler. Because it is a straight linear tube rather than a U-bend, it applies when the fixture is changed or is already a linear housing, not as a drop-in for a U-tube socket pair.
10) Our building is standardizing on 4100K lamps. Does the Sylvania 21878 match?
No. The Sylvania 21878 is a 3500K warm-neutral lamp at 82 CRI. A 4100K T8 such as the Philips 236794 is the cooler appearance, and mixing 3500K and 4100K tubes in adjacent fixtures will read as a visible color difference. Standardize the whole bay on one color temperature, and keep in mind the Philips lamp is a linear T8 while the 21878 is the U-bent format.
How fast can I get the Sylvania 21878 delivered?
Most orders ship the same day from our distribution partners, with quick delivery throughout the continental U.S. Need it urgently? Contact Us for expedited shipping options.
Can I return it if it doesn’t work for me?
Yes—ZenSupply offers a hassle-free return policy. If the product isn’t the right fit, reach out to our support team for a return authorization or setup a return by following our return instructions.
Does the Sylvania 21878 come with a warranty?
Absolutely. The Sylvania 21878 is backed by a manufacturer’s warranty. For full warranty terms, check the product documentation or Contact Us.
How do I get technical support or installation help for the Sylvania 21878?
You can call, text, or email our expert support team for fast answers. We’re here to help with product selection, installation tips, and troubleshooting. Contact Us
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