First there was the ST-33Q it used D cell batteries, then came the ST-33QR same specs but it used D-cells or the common Ridgid 18V rechargeable batteries a big advance really that saved you a lot of money. Now the new ST-33Q+ it is the same specs but has bluetooth so you can connect to your SR-24 locator and control the ST-33Q+ up to 200 yards away, change the freq. heck even turn it on or off if you forgot lol. I do not own one yet but will soon when I would have been buying just the ST-33QR.