HALF ROUND PIPE (CSP, CASP, CAP) For downslope drains, ditch liners, and areaways. Standard 10 foot lengths are furnished match punched with bolts. Also available in two foot increments in .064, .079 and .109 inch thick steel. Aluminum thicknesses are .060, .095 and .105 inch. PART CIRCLE CORRUGATED SHEET.