DiCon Fiberoptics Inc. has modified its Miniature Tunable Filter to include a captured o-ring sealed tuning screw for improved feel and precise tuning. The center wavelength can be tuned over 15 nm with 0.5-dB bandwidths as narrow as 0.8 nm. Additional benefits include 0.05-nm tuning resolution, 0.05-dB typical polarization dependence loss and 1-dB insertion loss. A new package design provides excellent environmental protection. The filter is suited for panel or printed circuit board monitoring.