Check the listing for details. BRISTOL MINI SPLINE WRENCH L-KEY SET FOR COLLINS & HALLICRAFTERS KNOBS SS-508. Condition: New. Listed at 24.95 USD. ONE NEW NINE PIECE SET Bristol SS-508 mini spline wrench set. Use to remove the knobs on many Collins and Hallicrafters radio equipment. These vintage radios used multi-fluted spline nuts on the knobs that are not compatible with a typical Allen wrench. The set includes the popular wrench diameter sizes (in inches) of 0.033 x 1.25"(L) (4 flute), 0.048 (4 flute), 0.048 (6 flute), 0.060 (6 flute), 0.069 (4 flute), 0.072 (6 flute), 0.076 (4 flute), 0.096 (6 flute), and 0.111 x 2"(L) (6 flute). Wrench length ranges from 1.25 to 2 inches. Includes vinyl carrying case. NOTE: The optional Vernier main tuning knob on the Collins 75A-4 uses a hex set screw. Not intended for use in adjusting transformer slugs which require longer length spline wrench. May not fit all knobs on select equipment so please verify the wrench size needed. Visit our eBay store for other radio accessories.