TM Series Carburetors provide significant performance improvements over older design round slide carburetors. Air flows faster and smoother through the TM Series venturi due to the flat slide configuration and the jet blocks which help create a smoothbore effect. The high velocity of the air flow means a stronger vacuum at the needle jet, providing more precise metering and better throttle response.
While the sku of this part is VM28-418, it shares the typical characteristics of the TM series flat slides. Many people call this the TM28, but the sku is not a mistake.