After both my wireless Acurite and LaCrosse anemometers failed, I decided to buy the HoldPeak 866B hand-held unit to calibrate a hard-wired anemometer I am building using an Arduino Mega connected to the mechanical parts of my defunct Acurite.The box containing the HoldPeak had one corner that was crushed. Fortunately, the unit itself, which was in a sealed plastic bag, was undamaged. The attached photos show all that was included - the unit, the zippered carrying case, the lanyard that screws into the tripod mounting hole, and the instruction sheet.Of course the unit would not power up right out of the box because the two included AAA batteries were wrapped in plastic. I used a jeweler's Phillips screwdriver to remove the two small screws holding the battery compartment cover. The cover itself required a knife blade to pry it out. Removed and unwrapped the batteries then reinstalled them. The unit now powered up.I found the included, bare-bones instructions somewhat ambiguous regarding the use of the MAX/MIN and AVG (average) buttons, I had assumed, based on the skimpy instructions, that after you completed a measurement, you could switch between MAX and MIN and see those two wind speeds displayed. Finally figured out that is not how they work. What the instructions don't say is to get the MAX wind speed, you first must press the MAX/MIN button so that MAX appears on the display. Then do your measurement. When you are finished, the display will show the maximum speed and hold it until you either turn the unit off, hit the MAX/MIN or AVG buttons, or take another measurement where the wind speed exceeds that shown on the display from the first measurement. I like this feature.You can take a reading without the MAX icon showing and, after you finish, hit the MAX button but the reading will not be the max speed that occurred but some lesser speed,Why the MIN (minimum) wind speed feature was included is beyond me. Because, let's face it, every measurement you make is going to have a zero minimum. And that is exactly what is shown (0.0) every time you begin a reading with the MIN icon showing on the display.Use of the AVG feature is also rather hokey. Before you do a measurement, you have to press the AVG button so that icon is displayed. Then make your measurement. The display will show the actual wind speed until you stop. Then the speed that is displayed will decrease to some value (probably the average) and hold there for about 5 seconds then begin to decrease down to zero. The only thing the instructions say about this is - "average reading in 15 seconds will be displayed".Despite the lack of detailed instructions on how to use the MAX/MIN and AVG features, I found the wind speed measurements to be quite accurate. I tested the unit several times at different speeds by holding it out of my car window with MAX showing on the display. As I drove, I kept an eye on my speedometer to note the maximum speed I attained. When I stopped and checked the reading, it was right on what my speedometer indicated. At least it was accurate up to a speed if 32 miles per hour, which is the fastest I have tested it so far. The instruction sheet indicates that the speed accuracy is +/- 5%, which appears to be true. The next time I hit the highway, I'll check it out at 65 mph.Also displayed at the bottom is the air temperature, which is switchable between °C and °F. The unit apparently has a wind chill feature that only works when the temperature of the unit goes below 0 degrees C (32 F). Again the instructions are vague on the subject. I had to go back to Amazon's listing of the unit to learn that, when the air temp is below 32F, the temperature reading changes from the actual air temp to the wind chill value. Being in Florida, I don't think I will ever have the opportunity to check it out. I'll leave that up to the poor devils up north.Another feature I like is the switchable backlight. Great for checking wind speeds at night.Finally, the bottom line is that the HoldPeak 866B does what I bought it for - to have an inexpensive hand-held anemometer that will measure wind speeds with some degree of accuracy.