The most critical factor is the material grade, which must be Food-Grade Stainless Steel 304 or 316L to ensure corrosion resistance against acidic beer and cleaning chemicals. You must also identify the fitting type required for your market, such as Type A (Flat), Type S (Well), Type G, or Type D (American Sankey). Additionally, verify the safety neck design (e.g., safety catch or safety lock) which prevents the spear from accidentally ejecting under pressure, a vital feature for operator safety.