Standard duty 5' long 2" angle ramps that is 3/16" thick.  This will handle most vehicles.  These are the same ones that some other places call "heavy duty", but you still need to order something stronger for certain loads such as really heavy tractors and skid steers.  Check the store inventory for heavy duty 1/4" thick ramps, extreme duty 3" channel ramps, expanded metal mesh covered ramps, and ramps with supportive feet for the ultimate in loading ease. Priced per pair.