| Hardware and OS | S-TELL M621 | Oppo A3s |
| Operating system | Android 6.0 | Android 8.1 (Oreo); ColorOS 5.1 |
| Processor | MediaTek MT6580, 1300 MHz | Octa-core 1.8 GHz Cortex-A53 |
| Chipset | | Qualcomm SDM450 Snapdragon 450 (14 nm) |
| Processor cores number | 4 | |
| GPU | Mali-400 MP2 | Adreno 506 |
| RAM | 2 GB | |
| Internal memory | | 16 GB, 2 GB RAM |
| Internal Storage | 16 GB | |
| External memory | | microSD, up to 256 GB (dedicated slot) |
| Memory Card Slot | yes, separate | |
| Display | S-TELL M621 | Oppo A3s |
| Type | colored IPS, 16.78 mln colors, sensor | IPS LCD |
| Size | 5" | 6.2" inc |
| Resolution | 1280x720 | 720 x 1520 px |
| Touchscreen | multitouch, capacitive | capacitive touchscreen |
| Screen-to-Body Ratio | | 81.2% |
| Display area | | 95.9 cm2 |
| Display aspect ratio | | 19:9 (height:width) |
| Aspect Ratio | 16:9 | |
| Pixel Density | 294 | 271 PPI |
| Automatic display rotation | yes | |
| Colors | | 16M |
| Connectivity | S-TELL M621 | Oppo A3s |
| Standard | GSM 900/1800/1900, 3G | |
| 2G Network | | GSM 850 / 900 / 1800 / 1900 - SIM 1 & SIM 2 |
| Interfaces | Wi-Fi, Bluetooth, USB | |
| 3G Network | | HSDPA 850 / 900 / 2100 |
| Multi SIM mode | alternate | |
| 4G Network | | LTE |
| SIM-card amount | 2 | |
| Wi-Fi | | Wi-Fi 802.11 b/g/n, WiFi Direct, hotspot |
| Network | | GSM / HSPA / LTE |
| SIM card | | Dual SIM (Nano-SIM, dual stand-by) |
| Bluetooth | | 4.2, A2DP, LE |
| Edge | | Yes |
| GPRS | | Yes |
| GPS | | Yes, with A-GPS |
| Speed | | HSPA 42.2/5.76 Mbps, LTE-A (2CA) Cat6 300/50 Mbps |
| USB | | microUSB 2.0, USB On-The-Go |
| Camera | S-TELL M621 | Oppo A3s |
| Main camera functions | autofocus | |
| Front camera | 5 megapixels | |
| Flash | rear, LED | |
| Video Recording | yes | |
| Main camera | 13 MP | 13 MP, Dual |
| Specs | | 13 MP, f/2.2, AF
-2 MP, f/2.4, depth sensor |
| Features | | LED flash, HDR, panorama |
| Video | | 1080p@30fps |
| Selfie camera | | 8 MP, Single |
| Multimedia | S-TELL M621 | Oppo A3s |
| Audio | MP3, FM-radio | |
| Headphone jack | 3.5 mm | |
| 3.5 mm Jack | | Yes |
| Radio | | FM radio |
| Design | S-TELL M621 | Oppo A3s |
| Case type | classic | |
| Height | 145 mm | |
| Width | 72 mm | |
| Thickness | 9 mm | |
| Colors | | Red, Dark Purple |
| Dimensions | | 156.2 x 75.6 x 8.2 mm |
| Weight | 180 grams | 168 g |
| Battery | S-TELL M621 | Oppo A3s |
| Capacity | 2350 mA?h | |
| Battery type | Li-Ion | |
| Connector type for charging | micro-USB | |
| Battery capacity | | 4230 mAh, Non-removable Li-Ion |
| Other | S-TELL M621 | Oppo A3s |
| Flashlight | yes | |
| Release date | | 2018, July |
| Sensors | approaching sensor | Accelerometer, proximity, compass |
