The Echo Trigger allows the shooter to select from 3 different settings: Safe Mode: Firearm will not fire.Semi-Automatic Mode: Firearm fires when the trigger is pulled.Echo Mode: Firearm fires when the trigger is pulled and also when the trigger is released.The Echo Sport trigger does not come with a bolt carrier. You will need a full auto bolt carrier in your firearm for the Echo Sport to function.#html-body [data-pb-style="62DF828AA1D95"]{justify-content: flex-start; display: flex; flex-direction: column; background-position: left top; background-size: cover; background-repeat: no-repeat; background-attachment: scroll; border-style: none; border-width: 1px; border-radius: 0px; margin: 0px 0px 10px; padding: 10px;}#html-body [data-pb-style="62DF828AA1DA2"]{border-style: none; border-width: 1px; border-radius: 0px; margin: 0px; padding: 0px;}