Do You Need a Rear Cam? 70mai RC21 vs RC22 Compared

Quick answer

The RC21 and RC22 are functionally the same rear camera: both record 1080P at 130° with an F2.0 aperture and a 6.0-meter cable. The only real difference is compatibility. The RC21 fits the 70mai Dash Cam A410, T800E, T400, and A810 Lite, while the RC22 fits only the 70mai Dash Cam 4K A800SE. Buy the one that matches your front camera, and don't expect a rear cam to improve front-facing footage.

What actually differs between the RC21 and RC22

On paper, the two rear cameras are twins. Both capture 1080P video through a 130° lens with an F2.0 aperture, and both ship with a 6.0-meter cable for routing from the front windshield to the rear of the car. Neither is a 4K unit, and neither is weatherproofed for exterior mounting. The difference is the connector and firmware pairing inside the housing, which is why 70mai splits them into two SKUs rather than one universal accessory.

That means your decision is not about image quality. It is about which front dash cam you already own. If you have an A410, T800E, T400, or A810 Lite, the RC21 is the correct part. If you have an A800SE, the RC22 is the only one that will work. Mounting a mismatched unit will not simply degrade the picture; it will fail to initialize.

Do you actually need a rear camera?

A rear camera is worth adding when most of your risk sits behind the car, not in front of it. That includes commuting in stop-and-go traffic where rear-end collisions are common, driving a vehicle with poor rear visibility, or parking in lots where someone could back into you while you are away. In those cases, the rear view is the only view that matters for the incident you are most likely to have.

It is less useful if your main concern is road-trip scenery or forward-facing lane footage. A rear camera also adds a second cable run, which is the most time-consuming part of the installation. If you are not comfortable pulling trim panels, budget for professional installation or choose a vehicle where the cable can be tucked along the headliner and door sills without removing seats.

Installation and cable routing for either model

Both cameras use the same 6.0-meter cable, which is long enough for most sedans, SUVs, and small vans. Route it from the front camera along the top of the windshield, down the A-pillar, under the door sill trim, and up behind the rear seat to the rear glass. Avoid running it next to factory wiring harnesses where possible, and leave a small service loop at both ends so vibration does not pull the connector loose.

Before you buy, check whether your front camera already has a rear-camera port. The A410, T800E, T400, A810 Lite, and A800SE all support one of these two units, but the port and firmware must match the specific model. If you are unsure, confirm your exact front camera model number from the label on the mount or in the app settings before ordering.

Should you add a CPL filter at the same time?

A circular polarizing filter is a separate upgrade that reduces windshield reflections and boosts color saturation in bright sun. The 70mai CPL Filter fits the A410, A510, A800SE, A500S, and Lite 2, so it overlaps with some of the same cameras that accept the RC21 or RC22. One caveat from the manufacturer: the tinting film on your front windshield may reduce how well a CPL filter works. If you have aftermarket tint on the front glass, test the filter before committing to a long road trip.

A CPL filter does not replace a rear camera and a rear camera does not replace a CPL filter. They solve different problems: the filter cleans up glare through the front glass, while the rear camera captures a second field of view. If your budget only covers one, pick based on whether your biggest risk is sun glare in front or an impact from behind.

Trade-offs to weigh before you buy

• Compatibility vs. universal fit: The RC21 and RC22 are model-specific, so you cannot buy one and move it between cars with different 70mai front cameras. Match the rear cam to your exact front camera model before ordering.
• Coverage vs. installation effort: A rear camera adds a second 6.0-meter cable run through the cabin, which is the slowest part of the job. Budget an extra hour or pay for professional routing if you are not comfortable removing trim.
• Rear coverage vs. front clarity: Spending on a rear cam does not improve front footage; a CPL filter addresses glare and color on the front camera instead. Choose based on whether your main risk is behind you or in front of you.

Product facts at a glance

• 70mai Rear Camera RC21 for Dash Cam A410/T800E/T400/A810 Lite: Only compatible with the 70mai Dash Cam A410, T800E, T400, and A810 Lite, with 1080P recording, a 130° viewing angle, F2.0 aperture, and a 6.0-meter cable. If you own one of those four front cameras, this is the rear unit to buy; it will not work with an A800SE.
• 70mai Rear Camera RC22 for Dash Cam 4K A800SE: Only compatible with the 70mai Dash Cam 4K A800SE, with 1080P recording, a 130° viewing angle, F2.0 aperture, and a 6.0-meter cable. A800SE owners need this specific SKU; the RC21 will not connect even though the specs look identical.
• 70mai CPL Filter for Dash Cam A410/ A510/ A800SE/ A500S/ Lite 2: Reduces windshield surface reflections and intense sun while enhancing color saturation; compatible with the A510, A800S, A500S, and Lite 2, and windshield tinting film may affect performance. A useful add-on for bright climates, but check your front tint first and confirm it fits your specific front camera.

Which rear camera should you choose?

Best for

• Drivers who already own a 70mai A410, T800E, T400, or A810 Lite and want rear coverage
• A800SE owners who need the matching RC22 rear unit
• Commuters and city drivers who want a record of rear-end collisions and parking incidents

Not for

• Drivers who want a single-camera setup and do not want to route a second cable
• Owners of front cameras outside the listed compatibility sets, who should confirm fit before buying
• Anyone expecting 4K rear footage; both units record at 1080P