The Straz Sealant Funnel makes adding tubeless tire sealant simple

Topping off tubeless tires with sealant is one of those tasks most of us conveniently forget, or avoid altogether. Injectors clog, hoses leak, and scooping sealant into the tire by cracking a bead feels downright prehistoric. Fortunately, there’s a simple tool for the job designed by rider and tinkerer Tim Straz that promises to make the process easier—and a lot less messy.

New Hampshire-based Straz says he designed his sealant funnel out of frustration. “I was sick of the mess,” he tells me. “Injectors are cumbersome and messy. The hoses often leak, and cleaning is a pain. The Funnel is just simpler, and it’s built to last.”

Simply enough, his product is called the Sealant Funnel, and it’s 3D printed with a threaded brass insert that attaches directly to most presta valve stems. Unlike plastic injectors that rely on a flexible hose that fits over the valve, the Sealant Funnel threads on securely so it won’t accidentally slip off or leak around the edges under pressure.

It works with most, but not all, tubeless tire valves

The standard version of the funnel worked well with most of the of valves I tested, including the Reserve Fillmore, Orange Seal VersaValve, and Stan’s Tubeless Exo-Core. I found it didn’t thread tightly onto the Clik valve or Muc-Off Big Bore valve, both of which lack a standard threaded body. For the Muc-off Big Bore valve, you’ll need to remove the top half to attach the funnel.

Straz makes another version of the funnel — the Sealant Funnel PT — that’s designed for use with partially threaded valve stems like the Reserve Fillmore and Stan’s Tubeless Exo-Core valves. The standard funnel also fit those valves well enough in my tests, though the PT offered an even better fit. Additionally, the PT version fits the Clik valve. Unfortunately, if you’re running Muc Off Big Bore valves, you’re out of luck, as neither the standard nor the PT funnel is a fit.

Given the variety of valves my bikes are running, I’d probably go with the Sealant Funnel PT as it’s the most compatible, though again, while it does fit standard valves pretty well, it’s not quite as secure as the regular Sealant Funnel.

The Straz Sealant Funnel has a 30ml fill line etched on the inside, which equals roughly one fluid ounce. That makes it easy to eyeball your dosage without reaching for a separate measuring cup or an injector.

No glugging

Pouring sealant directly into the funnel was surprisingly smooth. I expected the sealant to glug as the liquid drains into the tire — like when you add oil to your car engine using a funnel — but that never happened.

How quickly the sealant drains into your tire will depend on how thick it is, and as we’ve found in previous tests, there’s a wide range of densities and viscosities among tubeless tire sealants. An ounce of Orange Seal Endurance drains in about two seconds flat, while Muc Off sealant takes an excruciating 30 seconds.

OK, so I’m being overdramatic. But in all seriousness, the drain time multiplies if you’re mounting a new tire and need to put five to six ounces of sealant inside. Sealant injectors can get the job done faster, though they do struggle with thicker sealant formulations, some of which actually form clogs in the tubing.

Added 7/15/25: Straz tells me he likes to push some of the air out of the tire before pouring sealant into the funnel. Releasing the tire allows it to suck the sealant inside more quickly.

Low-mess, long-lasting construction

I generally use an injector when it’s time to add sealant, and every injector I’ve used gets gummed up eventually, despite doing my best to remember to clean up after every use. Straz notes that injectors generally have at least three parts, all of which need to be cleaned. The funnel, on the other hand, can be rinsed after use and doesn’t require disassembly.

When it comes to injectors with tubes that slip over the valve stem, I generally get a drip or two, though nothing crazy messy. With the Straz Funnel, I got zero drips. The only other zero-drip solution I know of is the Milkit injector, which features a thin hose that fits inside the valve stem.

I found I can also use the sealant funnel as… well, a funnel. Transferring sealant from a big bottle to a smaller one or creating your own custom blend is messy if you don’t already have a funnel in your toolkit.

The patent-pending design features a threaded brass insert that should last a long time, and because there are no hoses, seals, or moving parts, there’s nothing to break or wear out. Priced at $17.99 ($18.99 for the PT version), the Sealant Funnel costs a couple bucks more than most injectors but should last longer.

Bottom line

Available in four colors, the Sealant Funnel is a small but welcome upgrade for anyone running tubeless. If you’re still using a scoop or fighting with a sticky injector, this might just be the fix you didn’t know you needed.