The items you are counting must weigh very similar amounts. The fact is, no counting scale (cheap or industrial quality) will ever function with any high degree of accuracy if there is a significant variation in the weight of the items that you're trying to count. One tip that we can offer you is this; the larger the initial sample (30 pieces versus 5 pieces) the better results the counting scale can provide since it averages out any variations in the piece weights for accuracy. Of course the trade off with this is that you must count out a sample of 25 pieces without human error which can be a challenge sometimes. Another note, to consider is capacity. Many customers buy a counting scale with more capacity than they typically need. The reason they do this is usually just "I thought it made sense to buy the max capacity". If the majority of the time you're counting no more than ten pounds of parts at a time, then a 10 lb. capacity counting scale is a great choice for you. If you need larger capacity options, you can choose a couple of different capacities, or buy a scale with accumulation function, or buy a model with remote scale capability. You are also welcome to contact us with your scenario and we can tell you what are the best counting scales and provide reviews and recommendations.