Multi-bit drivers used to suck but have been greatly refined in recent years. Case in point—Klein's HVAC 8-in-1 Hex Head Slide Driver. To look at it you would think it's a nut driver, which for some reason has a knurled sleeve behind the head. But why?
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The sleeve is a threaded lock for the magnetic head. Slide the head forward and it drives 5/16" hex fasteners; slide it back and it drives 1/4" hex fasteners—the most frequently used sizes in the HVAC (heating, ventilation, and air conditioning) trades. It's fast and convenient to use a sliding head because nut sizes can be changed without reversing the shaft or installing different sockets.
The shaft can be pulled from the handle and reversed to expose a hollow end that fits 3/8" hex fasteners. A reversible hollow sleeve fits inside and can be used to hold or store a pair of reversible 1/4 hex shank tips, or used by itself to drive 1/4" hex head fasteners.
The loose parts at the bottom store in the shaft.
Tips include #2 Phillips, 1/4" and 1/8" flat, and a bit to adjust TR-4 Shrader valves. You may be unfamiliar with the term but you have certainly seen a Shrader valve; it's the mechanism inside the valve stem of a bike or auto tire. The same type of valve is used for HVAC applications such as pressure testing gas lines and charging AC and refrigerator compressors.
There's nothing sacrosanct about the combination of hex shank tips that come with the HVAC 8-in-1 Hex Head Slide Driver; they could easily be swapped out for ones better suited to other tasks or trades.
This is a clever configuration that allows the HVAC mechanic to use a single tool for 8 types of fasteners and fittings. In a shop setting it might make sense to use 8 different tools but when working out of a tool pouch—as tradespeople frequently do on the jobsite—it's best to travel light and perform as many tasks as possible with a single tool.