Final answer:
Flared joint fittings are most commonly associated with type K annealed copper tubing, which is designed to withstand higher pressures and is thicker than other types of copper tubing.
Step-by-step explanation:
Flared joint fittings are typically used with type K annealed copper tube. Type K copper tubing is thicker than type L, M, and DWV, making it suitable for the high pressure that flared fittings must withstand. The flaring process provides a larger surface area for the seal, which is particularly effective for the high-pressure and temperature changes often encountered in certain applications such as HVAC, gas supply, and high-pressure fluid transmission.