Overview Reviews Product Description Single groove aluminum adjustable sheave for 4L - "A" (1/2") & 5L - "B" (21/32") type V-beltsOpening/closing the pulley increases/decreases the speed at which the belt rotatesLight duty applications only*, use cast iron or steel sheaves for harsher environment applications Dynaline Catalog Product Videos Custom Field Product Reviews Write a Review Write a Review × Dynaline Aluminum Variable Speed Sheave 3-1/4 x 1/2" 55490 Rating * Select Rating 1 star (worst) 2 stars 3 stars (average) 4 stars 5 stars (best) Name Review Subject * Comments *