Working on your STIHL chainsaw or trimmer? This little tool is a lifesaver! It's the official STIHL carburetor limiter cap tool, part number 5910 890 4500 (also shown as 5910-890-4500). What's it for? Many STIHL carbs have plastic limiters on the adjustment screws (the ones marked H and L for high and low speed) to prevent owners from tuning them too rich or lean. If you need to do a proper carb adjustment – maybe after breaking in the engine or changing altitude – you need this special tool to remove or turn those limiters. It's brand new in its original STIHL packaging. A must-have for any STIHL owner who does their own maintenance, small engine mechanics, or landscaping pros. It's a simple, durable, purpose-built tool that saves you from trying to jam a screwdriver in there and damaging something. Keep your saw running at its peak performance with precise fuel mixture adjustments. Just pop it on the limiter cap and turn. Essential gear for the serious STIHL user's toolbox.