More durable commercial walkie-talkies; can be used for a long time The RT21 walkie-talkie is a rugged, long-lasting radio; built to withstand harsh environments such as humidity, dust, vibration and extreme temperatures. The radio requires no licence and is easy to use; employees or staff do not have to worry about additional training to figure out these two-way radios. It can be used in a wide range of industries such as education, warehousing and logistics, security, hotels and churches; bringing the clearest and most reliable communication to your business! Ultra-Clear Long Range Reception Powerful penetrationHigh gain long antenna designup to 250,000 square feet or 25 floors Longe battery life Real 1100mAh lithium battery10-12 hours of battery life3.5 hours to fully charge Crystal clear audio quality Clear and loud audio outputBackground noise and static cancellation Rugged two way radio 2M free fallSolid durable back ClipThicker and more durable housing Secret service earpiece 360 degree rotating clipFinger PTT and sensitive microphoneProfessional and comfortable wearing experience Other features Channel 16 TOT time out time Squelch 0-9 level VOX Hands-free (requires activation to use) Low battery alert ＜10% Power saving function Automatic CTCSS/DCS Reduces unnecessary transmissions Emergency alarm Remote Working voltage DC 8V Working temperature -10℃~+50℃ Package Details: 10 x RT21 walkie talkies（2 boxes with 5 walkie-talkies each）10 x 1100mAh li-ion and charger10 x Belt clip and sling10 x Earpieces2 x English user manual Can RT21 talk to each other? Can they talk to other brands of walkie-talkies? Yes, they are ready to use out of the box and can talk to each other by selecting the same channel. RT21 cannot talk to other brands of radios What to do when the walkie talkie prompts"please change battery? Please note that the prompt tone is "please charge battery", not "please change battery"just place the walkie talkies on the charging base, the charging indicator shows red to indicate charging, and green indicates that it is fully charged Can the RT21 talk directly to the H-777/RT22/RT68？ Yes, the RT21 can talk directly to the H-777/RT22/RT68 and all Retevis FRS 16-channel radios and can talk directly to all Retevis FRS 2-channel radios What accessories are available? We offer earpieces, microphones, clips and batteries for the RT21