The Red TT40 is model you need if you buy it from Jett since the engine has 37MM spacing just like the EVO .40-.46NT, and .46-.52NX's, OS .46FX-55AX along with Magnum .46-.52's, TT .40-46's, Tower .46;s, and the list goes on. I am willing to bet that it is identical except for the color as the TT40 since the mounting pattern is the same. My .60NX along with my friends both turn over 15,000 (Not peak Rpm) with the TT40 and a 10-8. Mine is a little stronger turning 15,300, but I did a little clean up work to it. With a 10-7 it was over 16,000, and my buddy went running for cover, since he thought it would grenade. From the reading I am getting, it looks like a poor man's Jett engine for performance. These readings are with about four tanks of fuel through them. Dubb stated to me (a couple months ago) that it would be perfectly sized for the .60NX, since it is used with his .60L, along with the OS .55AX, as long as the spacing was 37mm, which I assured him it was. Buy which everone you can get cheaper, or color you prefer more.