The 8503-00 model is the blank version of the 8501-00 model (you make the string slots and determine the string spacing) to upgrade or replace the existing saddles on your Gibson Nashville Tune-o-Matic bridge dated after 2000.
These are also the saddles we load into our ResoMax NV2 Bridges and they are a drop-in replacement on tune-o-matic bridges with API stamped on the bottom!
Please note: engineered for maximum vibration transfer, TUSQ saddles for electric guitars will add rich bell-like highs and big open lows. Switching to TUSQ Tune-o-Matic saddles will add more "spank" to your tone.