Fits holes 1 inch to 1-1/8 inch diameter, mounting holes are on 1 1/2" centers. With separate mounting ring, so may be mounted on top or bottom of chassis. SPECIAL ORDER - PLEASE ALLOW 1 WEEK octal-goldcerch$10.95 Triode, USA Customer Service M-F 9AM-4PM CT 1-800-774-3201 Email us Anytime: questions@triodestore.com