Comparison · Fitness rings · Desk research
Circular Ring 2 vs Circular Slim
Side-by-side manufacturer cells from the two named ring pages. Not a lab test. Brand grouping uses the published brand field (Circular).
Quick Answer
Circular Ring 2 vs Circular Slim is a desk comparison of OEM cells (verified 2026-09-19 / 2026-09-19). Circular Ring 2: $299 sale / $349 list USD on shop.circular.xyz, 2026-09-19. Circular Slim: Not listed on shop.circular.xyz collections, 2026-09-19. Do not invent a leftover street ticket.. Battery: Shop spec: 8 days power mode, ~5 days performance. Shop FAQ (2026-09-19 evening… vs Up to 5 days; rechargeable 24–31 mAh Li-Ion, non-replaceable. Not a lab test.
The verdict
Circular Ring 2 for new buyers on this Circular line; Circular Slim if the leftover size, finish, or dated ticket is the fit
Why: Same brand (Circular). Circular Ring 2 ranks newer/current on this line. Cells are OEM quotes dated 2026-09-19 / 2026-09-19 — not a lab winner for comfort, accuracy, or real-world battery.
Buy Circular Ring 2 if
Buyers who want a single-lead ECG on a ring and will treat it as wellness, not diagnosis.
Buy Circular Slim if
Owners who already have Slim and want the official guide numbers in one place.
Specs side by side
Same rows as the two named ring pages. Values are copied from those pages — if a cell is unpublished or contradictory on the manufacturer page, it already says so.
| Attribute | Circular Ring 2 | Circular Slim |
|---|---|---|
| Materials | High-grade titanium with coating; non-allergenic clinical-grade biocompatible inner epoxy (guide)Circular Ring 2 user guide | Inner: non-allergenic, nonmetallic clinical-grade biocompatible resin. Changeable outer-shell (care section). Outer alloy not named on the fetched spec block (accessed 2026-09-19).Circular Slim user guide §16 / care |
| Width | 7.8 mmShop “by the numbers”; user guide dimensions | 8.8 mmCircular Slim user guide — Ring size & characteristics |
| Thickness | 2.55 mmShop; user guide | 2.2 mmCircular Slim user guide |
| Weight | 3 g (shop also uses “four grams” in one marketing line — we use the 3 g spec block)Shop spec block; user guide | 2 gramsCircular Slim user guide |
| Sizes | US 6–14 (nine sizes)Shop; user guide | 8 sizes, US 6–13Circular Slim user guide |
| Finishes | Silver, Obsidian, Gold, Rose Gold (shop). Sensors/battery identical across finishes.shop.circular.xyz/products/circular-ring-2 | Not listed as named colorways on the fetched Slim spec block (accessed 2026-09-19)Circular Slim user guide |
| Battery (OEM) | Shop spec: 8 days power mode, ~5 days performance. Shop FAQ (2026-09-19 evening): around eight days power / four to five performance. User guide: up to 7 days (power mode); 14.5–21.5 mAh Li-Ion.Circular shop spec + FAQ; user guideDo not average 8 and 7, or 5 and 4–5. Quote the page you are citing. | Up to 5 days; rechargeable 24–31 mAh Li-Ion, non-replaceableCircular Slim user guide §16 |
| Charging (OEM) | Shop: 30 minutes to full. User guide: up to 60 minutes from empty; 5 V; first-use calibration ≥45 minutes at 100%.Shop; user guide §07 | Spec: 60 min. Charging chapter (2026-09-19 evening re-pull): 45–60 minutes from empty at 5.5 V; first-use calibration ≥45 minutes at 100%.Circular Slim user guide §16 and charging chapterCite the section. Do not average with Ring 2’s shop 30-minute line. |
| Charging case (OEM) | Wireless charging case included; 700 mAh pack in the guide; size-specific; extra Case 2 sold for $39 on the shop. Charger is not waterproof.Shop; user guide | Magnetic charger (high-end polymer in the spec). Not Ring 2’s 700 mAh Case 2. Shop no longer lists a Slim charger SKU on 2026-09-19.Circular Slim user guide; shop.circular.xyz/collections/all |
| Water resistance | Not publishedUser guide — Waterproof / spec; shop FAQ | IP68: 5 m for a maximum of 30 minutes. Not recommended in salted water. Care section repeats the same 5 m / 30 min line.Circular Slim user guide — Waterproof / care |
| Sensors | Single-lead ECG; 3-axis accelerometer; digital temperature; 3-LED oximeter (IR, red, green)User guide — Ring Sensors; shop | 3-LED oximeter (IR, red, green); 3-axis accelerometer; digital temperature. I/O: tap-activated button + vibration motor.Circular Slim user guide §16 |
| Sleep tracking | Four-stage sleep, breathing rate, blood oxygen, morning score (shop). Up to 7 days flash memory depending on use (guide).Shop; user guide | Sleep analysis on the Circular app feature family (quality score, stages including deep and REM, on the shared Circular feature pattern). Quote the guide; Slim spec does not add ECG.Circular Slim user guide features / app |
| Activity / fitness | Activity and energy; live HR / SpO2 / temperature on demand (shop). Tight-grip sports can impair PPG (guide).Shop; user guide accuracy notes | Activity analysis / live HR / SpO2 on the Circular app. Tight-grip sports can impair PPG (guide accuracy notes on the Circular family).Circular Slim user guide |
| App | Circular app (iOS App Store, Google Play). Pair as “Gen 2” in the guide’s setup copy.User guide | Circular app (App Store and Google Play). Free app on the spec block.Circular Slim user guide |
| Subscription / data access | No mandatory subscription for core features (shop FAQ). Some advanced screens are premium and can be unlocked with coins earned by wearing the ring.Shop FAQ | Not publishedCircular Slim user guide compatibility |
| Phone platforms | iPhone (App Store) and Android (Google Play). Exact OS version floors not published on the fetched guide/shop pages.User guide; shop | iOS 11.0 or later, or Android 6.0 or laterCircular Slim user guide — Compatibility |
| Wireless | Bluetooth Low Energy 4.2 to 5.0 (guide); airplane mode listed on the shop spec blockUser guide; shop | Bluetooth Low Energy 4.2 to 5.0Circular Slim user guide |
| On-ring storage | Flash ROM up to 7 days depending on type and frequency of useUser guide | Up to 20 days of dataCircular Slim user guide — Memory Capacity |
| US price (dated) | $299 sale / $349 list on shop.circular.xyz, 2026-09-19Circular Ring 2 shop | Not listed on shop.circular.xyz, 2026-09-19shop.circular.xyz/collections/all |
| Price band | Mid, no mandatory data subscriptionDerived from dated shop | Discontinued compact ringDerived from missing shop listing + live user guide |
| Announced | Current Circular shop SKU as of 2026-09-19 (no Ring 3 retail spec page)shop.circular.xyz | Previous generation; Slim user guide still published 2026-09-19circular.xyz/user-guide-circular-slim |
| Availability | Shop live with worldwide shipping copy and US HSA/FSA note (accessed 2026-09-19)Circular shop | User guide live; shop collection is Ring 2 / Case 2 / accessories only (2026-09-19). Release notes: Slim deprecated.shop.circular.xyz; circular.xyz/release-notes |
Circular Ring 2 hub notes
- Single-lead ECG (~40 s) with PDF export; guide says wellness / not a medical device.
- No mandatory subscription for core features; shop says some advanced screens use earned coins rather than cash.
- Shop vs guide battery split is documented instead of averaged (8 vs 7 days; 30 vs 60 minute charge).
Ring 2 is the ECG-forward no-mandatory-sub ring: $299 sale / $349 list, 7.8 × 2.55 mm, 3 g, sizes 6–14, 50 m / 30 min in the guide. Buy it if you want on-demand ECG and will accept Circular’s wellness wording. Skip it if you need 100 m, a 10–14 day table, or a diagnostic ECG/BP device.
Circular Slim hub notes
- Official guide: 8.8 × 2.2 mm and 2 g — Circular’s thinnest published ring.
- IP68 to 5 m for 30 minutes (not salted water).
- Tap button + vibration motor; up to 20 days of memory.
Slim is the discontinued 2 g / 2.2 mm Circular: 5 days, 5 m / 30 min, vibration + tap button, free app on old OS floors. Use this page if you already own one. Buy Ring 2 if you want the current ECG titanium shop SKU.
Sources
Union of the two hub source lists. Re-open the OEM URL, not this comparison, to refresh a cell.
- Circular shop — Ring 2 — accessed 2026-09-19
- Circular — Ring 2 user guide — accessed 2026-09-19
- Circular — Slim user guide — accessed 2026-09-19
- Circular — user guide picker — accessed 2026-09-19
- Circular shop — all products — accessed 2026-09-19
- Circular — release notes — accessed 2026-09-19
Hub A: Circular Ring 2. Hub B: Circular Slim.