| Hardware and OS | Celkon A21 | Oppo A3s |
| Operating system | Android 4.2.2 (Jelly Bean) | Android 8.1 (Oreo); ColorOS 5.1 |
| Processor | Quad-core 1.3 GHz Cortex-A7 | Octa-core 1.8 GHz Cortex-A53 |
| Chipset | Mediatek MT6582 (28 nm) | Qualcomm SDM450 Snapdragon 450 (14 nm) |
| GPU | Mali-400MP2 | Adreno 506 |
| Internal memory | 512 MB, 256 MB RAM | 16 GB, 2 GB RAM |
| External memory | microSD, up to 32 GB | microSD, up to 256 GB (dedicated slot) |
| Display | Celkon A21 | Oppo A3s |
| Size | 4" inc | 6.2" inc |
| Type | | IPS LCD |
| Resolution | 320 x 480 px | 720 x 1520 px |
| Touchscreen | capacitive touchscreen | capacitive touchscreen |
| Screen-to-Body Ratio | 57.8% | 81.2% |
| Display area | 47.6 cm2 | 95.9 cm2 |
| Display aspect ratio | 3:2 (height:width) | 19:9 (height:width) |
| Pixel Density | 144 PPI | 271 PPI |
| Colors | | 16M |
| Connectivity | Celkon A21 | Oppo A3s |
| 2G Network | GSM 900 / 1800 - SIM 1 & SIM 2 | GSM 850 / 900 / 1800 / 1900 - SIM 1 & SIM 2 |
| Wi-Fi | Wi-Fi 802.11 b/g/n | Wi-Fi 802.11 b/g/n, WiFi Direct, hotspot |
| Network | GSM / HSPA | GSM / HSPA / LTE |
| SIM card | Dual SIM (Dual stand-by) | Dual SIM (Nano-SIM, dual stand-by) |
| 3G Network | | HSDPA 850 / 900 / 2100 |
| Bluetooth | 4.0, A2DP | 4.2, A2DP, LE |
| 4G Network | | LTE |
| Edge | Yes | Yes |
| GPRS | Yes | Yes |
| GPS | No | Yes, with A-GPS |
| Speed | HSPA | HSPA 42.2/5.76 Mbps, LTE-A (2CA) Cat6 300/50 Mbps |
| USB | microUSB | microUSB 2.0, USB On-The-Go |
| Camera | Celkon A21 | Oppo A3s |
| Main camera | 3.15 MP, Single | 13 MP, Dual |
| Specs | 3.15 MP | 13 MP, f/2.2, AF
-2 MP, f/2.4, depth sensor |
| Video | Yes | 1080p@30fps |
| Selfie camera | 1.3 MP, Single | 8 MP, Single |
| Features | | LED flash, HDR, panorama |
| Multimedia | Celkon A21 | Oppo A3s |
| 3.5 mm Jack | Yes | Yes |
| Radio | FM radio | FM radio |
| Design | Celkon A21 | Oppo A3s |
| Colors | Black, Blue, Red | Red, Dark Purple |
| Dimensions | 124.8 x 66.1 x 10.8 mm | 156.2 x 75.6 x 8.2 mm |
| Weight | 115.3 g | 168 g |
| Battery | Celkon A21 | Oppo A3s |
| Battery capacity | 1500 mAh, Li-Ion | 4230 mAh, Non-removable Li-Ion |
| Battery life | Stand by time- Up to 120 h (3G)
Talking time- Up to 8 h (3G)
| |
| Other | Celkon A21 | Oppo A3s |
| SAR | SAR EU - 0.99 W/kg (head) 1.39 W/kg (body) | |
| Release date | 2014 | 2018, July |
| Sensors | Accelerometer | Accelerometer, proximity, compass |
