Theta TO551 Collimator — Black

The TO551 is a red/green dot sight in a metal body, designed for 22 mm Picatinny/RIS rails. At 105 mm long and 215 g, it is aimed at shooters and hunters looking for fast target acquisition at close to medium range without giving up a solid build.

The choice between red and green reticle is not purely cosmetic: green is easier to read in bright light or against light backgrounds, while red tends to stand out better in low-light conditions. The multiple brightness levels let you match the dot's intensity to ambient lighting without losing contrast on the target. Four LR44 batteries is a common power solution in this category — easy to source, but worth keeping in mind compared to CR2032-powered sights that run on a single cell.

The holographic-style profile provides a more generous sight window than traditional compact red dots, making it easier to shoot with both eyes open. The trade-off to consider is weight: 215 g is on the higher end for an open reflex sight, which matters on lightweight platforms where the overall balance of the weapon system is relevant. Windage and elevation are adjustable by hand, so you can zero the point of impact after mounting without additional tools.

Key features

• Dual reticle colour — red or green — to suit different lighting conditions without swapping sights
• Multiple brightness levels to keep the dot visible in full sunlight or shade
• All-metal body at 215 g, built to handle repeated use on recoiling firearms
• Compatible with standard 22 mm Picatinny/RIS rails, no adapters needed on AR platforms, pump-action shotguns or carbines
• Windage and elevation adjustment to centre the point of impact after mounting

In the box

• TO551 collimator
• LR44 batteries
• Cleaning cloth
• User manual