: Typically used in unpressurized or low-pressure environments (up to approx. 0.5 bar). 2. Core Design Types
Includes an additional "wiper" or dust lip to prevent external contaminants from entering the system. Type B / BS: din 3760 pdf
A: Those are based on DIN 3760. "B" = Metal case, "A" = Dust lip, "BSL" = Heavy-duty spring. The standard defines these codes. "A" = Dust lip