Context:I am a adult male, 5' 10", ~175lb, with about 10% body fat. I've been tracking my physical measurements for about five years now, just to keep tabs on things. Since I have low body fat and high muscle mass, BMI isn't a great indicator of healthiness, so instead I've been using the Navy body fat formula -- BF% = 86.010 x log10 (waist - neck) - 70.041 x log10 (height) + 36.76 -- for measurements in inches, or -- %BF = 495 / ( 1.0324 - 0.19077 * log10( waist - neck ) + 0.15456 * log10( height ) ) - 450 -- for centimeters. This has given me consistent and what seem to be reliable results, +/- 3%, but it is sensitive to small changes in measurement (i.e. 1/8" variance is equal to about 0.3% BF) and I wanted to test the outcome against a second method to see if they were accurate in addition to being precise.Use:The Accu-Measure Fitness 3000 calipers are easy to use; they have a simple, functional design which will work for most people. The way it works is that the calipers have a slider, which you reset before the measurement. When you take the measurement, you squeeze the caliper together - thus pushing the slide along its rail - until the tab of the little arm clicks into its socket. When you release the pressure, the caliper returns to its open state, but the slide stays put, and you can read the measurement off the rail. All the calipers do is measure the thickness of the skin-fold inserted between the caliper pads, in millimeters. An included chart allows you use that measurement to estimate your body fat %. You can take one measurement - at the suprailliac (supra-illiac) right above the hip-bone, or four from the suprailliac, abdomen, triceps, and thigh, or even more, and use a calculator online to determine body fat % from that. You should probably take the measurement before any exercise or meals, to reduce the possibility of interference from transient factors.Review:I found the calipers very easy to use, though it is still tough to take some measurements without a partner. The suprailliac is easy, as is the abdomen and the thigh, but the triceps is tricky, as is the subscapular measurement on the back. Also, while this is still usable for someone with my body fat content, it's already a little marginal. Taking one suprailliac measurement returned a bf% of 11%, but taking four returned 8%, and a different four returned 5%, which is definitely wrong. So you need to take a few measurements and average them out. If you watch a couple videos on the subject, you'll understand how it works very quickly. The slider/rail system, paired with the click-arm, means you can get consistent results and takes a lot of the guess work out of use.So I think I'd recommend this for general BF% tracking, maybe in conjunction with the Navy formula, which is easier to calculate for oneself.