What They Have in Common
Both rangefinders hit ±1 yard accuracy, run at 6x magnification, include slope with a legal-play toggle, and use lithium batteries (CR2 in the Blue Tees, CR123 in the TecTecTec). Neither is rechargeable — you're swapping batteries, not plugging in. Both confirm flag lock with vibration feedback.
Where They Differ
Display: OLED vs LCD
This is the one that matters most day-to-day. The Series 4 Ultra runs an OLED display with brightness control. OLED screens produce true blacks and noticeably better contrast than LCD panels, which means the yardage is actually readable when you're standing in mixed shade and sunlight — the scenario every golfer is actually in. The ULT-S uses an LCD, which is standard for the category but is standard for a reason: it works. It's just not going to pop the way OLED does. If you've ever squinted at a rangefinder in the wrong light, you know this isn't a minor thing.
Stabilization and Flag-Lock Range
The ULT-S has optical image stabilization. The Series 4 Ultra doesn't. OIS reduces the visual shake when you're holding the rangefinder up — and if your hands aren't perfectly steady (nobody's are, especially on the back nine after a rough stretch), it makes locking onto a flag genuinely easier. The ULT-S also has a longer flag-lock range at 450 yards versus the Series 4 Ultra's 350 yards. Most approach shots happen well inside 200 yards, so the range ceiling won't matter often — but on a long par 5 where you're trying to figure out layup distance, those extra 100 yards of flag acquisition could matter.
Water Resistance and Build
Blue Tees rates the Series 4 Ultra at IP54, which is a real dust-and-water ingress rating. The ULT-S is described as rainproof, which is a softer claim — it'll handle light rain but it's not rated to the same standard. If you regularly play in the Pacific Northwest or tee off in the kind of October morning where everything is wet before the round starts, IP54 gives you more confidence. It's not waterproof either, but there's a difference between a number on a spec and a marketing descriptor.
Slope Toggle Design
Both have legal-play slope switches, but they work differently. The Series 4 Ultra uses a physical switch on the unit. The ULT-S uses a slope-switch faceplate — a removable panel that disables slope mode. The faceplate approach means you're less likely to accidentally toggle it mid-round, but it's also something you can lose. Call it a wash, but if you're the kind of player who always loses the small thing in the bag pocket, keep that in mind.
Who Should Buy Which
Get the Blue Tees Series 4 Ultra if:
- You play early mornings or late afternoons when light angles are awkward and a better display actually makes a difference
- You want IP54-rated water resistance instead of a vaguer "rainproof" claim
- You're buying one rangefinder to use for five-plus years and want the build quality to match
- You play somewhere with real weather — wind, mist, occasional rain — and don't want to baby your equipment
Get the TecTecTec ULT-S if:
- Your hands aren't steady enough to lock onto a flag quickly and you want OIS doing some of the work
- You play long courses where approach shots over 350 yards aren't unusual and you want flag-lock range to match
- You're a mid-to-high handicap player who wants a reliable, accurate rangefinder without overthinking the display specs
- The fog mode matters to you — early morning tee times on courses where the mist sits on the fairways
The Bottom Line
Twenty dollars is not the deciding factor here. The real question is: what do you actually need the rangefinder to do? The Series 4 Ultra wins on display quality and weather resistance — two things you'll notice every round. The ULT-S wins on stabilization and flag-lock range — two things that matter more if your hands shake or you're regularly trying to lock flags from 400 yards out.
Honestly, for most players, the OLED display and IP54 rating make the Series 4 Ultra the more complete package at essentially the same price. But if you've ever struggled to hold a steady lock, don't talk yourself out of the OIS.
Get the Blue Tees Series 4 Ultra.
See Also