Those are 18 and 19 mm string spacing bridges that pablopepper linked. The bridge supplied in my IB-5 kit had 17mm string spacing, but measure yours, it might be different. Watch out for a wider spacing as it would push the strings closer to the edge of the neck.

(measure from the middle of the saddle notches. The distance from the first to the 5th, divide by 4 (5 string bridge).)