Our selection of bronze nipples is limited, so we offer brass as well.The brass nipples that we offer are for above-the-waterline use only. 1/8"-3/8"dia. are yellow brass. 1/2"dia. and up are red brass. Due to the difference in nobility between brass and bronze, which can result in galvanic corrosion (and a failure of the fitting), we recommend that you not use these alloys together in saltwater environments. For reasons of safety, we suggest the use of cast bronze or Marelon tailpieces and hose instead.Barrel NipplesWhere not specified, the nipples we offer are "barrel" nipples, which consist of a smooth length of pipe that is threaded at each end. For these fittings, "Length" refers to the overall distance from end to end.Close NipplesFittings specified as "Close Length" are short fittings that are threaded along their entire length. Removal of "close" nipples with a standard pipe wrench will almost always damage the threads. To avoid damage, a nipple wrench, also known as an internal pipe wrench, which grips the inside of the fitting must be used.Threads are tapered "NPT", which stands for "National Pipe Thread".