Backing Plate f/70 Series Rod Holders. Backing plates are very important to have under every rod holder used for heavy tackle fishing. When the rod holder is under extreme load, regular nuts and washers can concentrate stress and cause spider cracking around your rod holders or perhaps even tear through causing severe gunnel damage. Smith backing plates distribute mounting bolt pressure evenly over 30 times more surface area than with standard washers alone. 2 sizes, one for 70 series and 80 series rod holders. Each size fits all 3 models of the Series. Features. Use this backing plate for all 70 series rod holders 53670A, 53670CA, 53671A, 53671CA, 53672A, 53672CA . 316L cast stainless steel. 4 x 5-1/4 . 4mm thick. Use your 1/4 stainless bolts and nuts hardware not included Backing plates are very important to have under every rod holder used for heavy tackle fishing. When 4 x 5-1/4 . 4mm thick