Optihaler by Healthscan has the advantage over other spacers because its unique design allows for an active mixing of medication with air. It directs particles away from the mouth, mixes them in several stages with air, then filters out the larger, less desirable particles. This results in a significant increase in the deposition of medication in the lungs. For safety from contamination, it has caps for each opening. In addition, patients rated Optihaler most convenient to use. Its very handy size measures 5" long and 1.75" wide.