There are three types of tuna that are used to make tekka rolls.
Bigeye tuna is probably the most common. It’s sometimes called ahi tuna.
Yellowfin tuna is the cheapest type of tuna for sushi. Confusingly, it’s also sometimes called ahi tuna. Yellowfin has the fishiest flavor of the three types.
Finally, bluefin tuna is the most prized for tekka sushi rolls. Only the lean cuts like akami will be used for tekka maki however.