Recently, I was on the hunt for the best preflop solver solutions and discovered GTOPACKS
https://gtopacks.com/en/ [gtopacks.com]. Their approach to 3-bet sizes in non-multisize strategies is truly remarkable. For example, for an open raise size of 2.5x, they offer solutions with 3-bet sizes of 9, 10, 10.5, 11, and 12 bb for both SB and BB positions. This level of detail is something I hadn't seen with other providers. Using their solutions has significantly improved my game. If you're serious about poker, GTOPACKS is the way to go.