LEIGH multiple mortise and tenon attachment replaces the dovetail assembly of your jig to make perfect through or blind tenons, box or finger joints. Includes complete instruction booklet and 1/2" spiral cut router bit for joints 1/2" x 5/8" to 1-1/2" x 2-1/2". Jig requires 5/8" OD guide bushing to operate. For small joints to 5/16" x 5/8" a 5/16" spiral cut router bit and 7/16" OD guide bushing are required (not included). Fits both D4 and D4R models.