There are many types of vials with most being yellow. Yellow vials are for general around the home use. Blue vials are for people needing superior accuracy, visibility and durability. See anatomy of a vial for more information.
Levels have a number of work surfaces. The primary work surface is on the thinner sides. These sides can be made of a variety of materials, often depending on the material of the frame. The very best levels have milled edges to maximize the flatness of the work surface.
Also, very good levels can be used on their sides as well. To learn more, see the 10 working positions of a level.
There are as many hand grip types as there are levels. For occasional use, grips don't matter that much. But for pro's that use their levels often, a good grip can make the difference between sore, tired hands and comfort. Look for dual density grips or very smooth extruded hand grips for the best fit.
PROTECTIVE END CAPS:
Levels are precision instruments that need to be handled with care. But we all know accidents happen. That's why each of our levels has protective caps. These caps absorb impact and protect the vial from damaging shock. The best professional levels have accordion style ''shocks'' which provide maximum protection.
Levels are generally made of plastic, aluminum or wood. Plastic levels are inexpensive and adequate for simple, around the house jobs. Entry level consumer grade aluminum levels are also very affordable, but provide longer life and better accuracy. If your customer can afford it, this is a much better choice, even for simple projects. Professional levels are made of wood or aluminum and are much more ridged and durable. The superior materials used in these products will assure longer life and greater accuracy. The best levels are easy to notice… they have blue vials.