H503c AA LH351D 4000K Neutral White High CRI Flood Headlamp

Product Description
A compact single-AA flood light built around a Samsung LH351D emitter at 4000K with 90+ CRI. Pure 120-degree flood beam with no hotspot — clean, even light right where you're working. At just 1 oz without a battery and under 2.8" long, this is about as small and light as a proper headlamp gets. Three programmable main levels from 264 lumens down to a 0.01 lumen moonlight mode that stretches over three months on a single AA. Unibody aluminum, sealed and potted electronics, IPX8 waterproof. Runs on a single AA NiMH, lithium, or alkaline cell.

Emitter: Samsung LH351D — 4000K, 90+ CRI, 3-step tint deviation

Output & Runtime (ANSI OTF, tested with Eneloop Pro AA)
High — H1: 264 lm (0.9 hr) | H2: 220 lm (1.6 hr) / 158 lm (2.3 hr) / 97 lm (4.2 hr)
Medium — M1: 52 lm (8.5 hr) | M2: 24 lm (21 hr) / 9.6 lm (41 hr) / 3.3 lm (4.5 days)
Low — L1: 1.0 lm (13 days) | L2: 0.25 lm (1.1 mo) / 0.06 lm (2.2 mo) / 0.01 lm (3.3 mo)
Beacon/Strobe — 0.2Hz beacon at Low | 0.2Hz beacon at H1 | 4Hz strobe at H1 | 19Hz strobe at H1
Remaining battery power (10–20%) after step-down is not counted toward runtimes.

Beam: 120° pure flood

Battery: Single AA — NiMH, lithium, or alkaline (Eneloop or Eneloop Pro recommended, not included)
Operating voltage: 0.7V–2.0V | Parasitic drain: negligible

Build
Unibody aluminum, precision machined from bar stock | Type III Class I hard anodize | Tempered optical grade glass | Sealed and potted driver | Reverse polarity protection | IPX8 waterproof (2m, 30 min)

Dimensions: 0.86" head diameter × 2.76" length

Weight
Head only: 1 oz (29g) | With battery: 2 oz (55g) | With battery and headband: 2.8 oz (78g)

Other
All levels current regulated | Battery capacity indicator (4 clicks from off, LED flashes 1–4 times) | Auto step-down at low battery | Electronic soft-touch switch | Proprietary heat sinking bonds LED board directly to unibody casing | Tailcap lockout by loosening

Operations
This light has 3 main levels (High, Medium, and Low) and a beacon-strobe mode. Each main level can be programmed to one of its two sub-levels, and the second sub-level of each main level can be further programmed to different brightness levels.

Basic Operation
1 click — Turns the light on to High, or turns it off.
2 clicks — Turns the light on to Medium.
3 clicks — Enters beacon/strobe mode.
Press and hold (0.6s+) — Turns the light on to Low, then cycles through Medium and High. Release at the desired level.

Advanced Operation & Configuration
Press and hold to cycle from Low → Medium → High. The cycle always starts from Low regardless of your current level. Release at the desired level.
Double-click at any main level to toggle between its two sub-levels (H1/H2, M1/M2, L1/L2). Sub-level selections are memorized through power cycles and battery changes.
To program the second sub-level (H2, M2, or L2) to a different brightness: double-click 6 times at that main level to enter configuration. Each subsequent double-click cycles through available brightness levels. Single click to save and exit. Settings are memorized through power cycles and battery changes.

Battery Indicator — From off, 4 quick clicks. The main LED flashes 1–4 times to indicate remaining battery capacity.

Beacon/Strobe — 3 clicks from off to enter. Double-click to cycle through beacon and strobe options. Settings are memorized through power cycles and battery changes.

Mode Groups
This light has three mode groups: G5 (factory default), G6, and G7. From off, select with 5 clicks (G5), 6 clicks (G6), or 7 clicks (G7). Selections are memorized through power cycles and battery changes.

All mode groups share the same basic controls:
H can be either H1 or H2 | M can be either M1 or M2 | L can be either L1 or L2
From off: 1 click → H | 2 clicks → M | Press and hold → cycles L, M, H

G5
H1 fixed | H2 programmable
M1 fixed | M2 programmable
L1 fixed | L2 programmable

G6 & G7 — All six levels (H1, H2, M1, M2, L1, L2) are fully programmable across 12 available brightness levels. Double-click 6 times at any level to enter programming mode. Double-click to go up one level, triple-click to go down. Single click to exit.

Factory Reset — Three consecutive 5-clicks (or 6-clicks, 7-clicks) from off resets G5 (or G6, G7) to factory defaults.