I use Warne rings/bases on my T3. They are groved for the top of the dovetail reciever on the Tikka. The ring and base are one unit (one for the front, one for the back). The front base/ring has the locating pin and the rear fits where you want it. I got mine at Epps and it was around $70-$80 if I remember correct. Cheaper alternative to the Opti-Locks. I hope this helps
Digger