Image Item No. Description  20952  Brick, Round 1 1/2 x 1 1/2 x 2/3 Dome Top Catalog: Parts: Brick, Round  553  Brick, Round 2 x 2 Dome Top Catalog: Parts: Brick, Round  553a  Brick, Round 2 x 2 Dome Top without Bottom Axle Holder Catalog: Parts: Brick, Round  79850  Brick, Round 4 x 4 Dome Top with 2 x 2 Recessed Center Catalog: Parts: Brick, Round