If using pellets in the magazine, do not use any type of pin style probe with a reduced front diameter. Damage to the pellet skirts will occur as the mag cycles. Any type of probe is acceptable when using slugs. The magazine will not feed Flat top pellets. Only Diabolo style pellets or slugs can be used in the magazine. The magazine will not properly stage pellets (in the STUD Pocket) with oversized diameters, such as JSB DIABOLO EXACT MONSTER 25.39g etc. STUD Magazines are designed for standard diameter pellets/slugs only. The magazine will not feed really short slugs like 25g Zans. These slugs do not have enough of the slug main diameter, to feed correctly.