With this sole installed on the Dual-Feed Foot, the fabric can be smoothly fed while piecing a uniform 1/4" seam allowance. A Digital Dual Feed Foot (BLTY-DDF) is required to use this sole. For Models: BLSA, BLDY, BLTY, BLJA, BLCR, BLAR (BLJY and BLAE with Digital Dual Feed foot).