This is a 7 piece Fillet Weld Gauge Set, a specialised set of gauges to check fillet leg and throat size.
Whilst multipurpose gauges are very good, the best way to measure fillet weld size and throat thickness quickly and accurately is with fillet weld gauges.
These fillet weld gauges come in a pack of seven gauges held together by a chain. Each blade is made of cold rolled stainless steel to resist corrosion and bending. They are double ended so you can measure 14 different fillet sizes from 3mm to 25mm for both throat thickness and leg length.
These robust fillet weld gauges should be part of every welders and welding inspectors tool kit.