Forty-one filament kits were measured for filament application force, single and multitester application force repeatability, and comparison of filament repeatability with that of other hand held instruments. Results of this study show that if their lengths and diameters are correct, the filaments produce application forces that are repeatable within a predictable range. All hand held instruments vary in application force. The Semmes-Weinstein monofilaments vary relatively little and are a controlled reproducible force stimulus for use in clinical testing.