Our UL Non-Kink Flexible PVC hose, commonly referred to as UL size, US size, UL non-kink, UL kink free tubing, UL water garden hose, UL pond tubing, and UL corrugated tubing is perfect for use with water gardening, ponds, waterfalls, fountains, aquariums and fish hatcheries, drains, light farming and gardening and light irrigation. This hose is designed to be used with barbed or insert fittings and appropriate clamps. The US or UL sized tubing is slightly larger than our MM or Metric sized pond tubing. If you are not certain which size to order, it is usually better to order the UL size and build up your fitting or pump outlet since the MM size is smaller and may not fit your application. While it is not as strong and durable as our flexible PVC pipe, it is somewhat more flexible and lighter. It will not collapse due to back pressure or from reasonable weight from cover material or gravel. Corrugated on the outside for strength and smooth on the inside to speed water flow, reduce material build-up and reduce friction, this lightweight tubing can easily be routed in any direction necessary without the use of multiple fittings. It can be used in areas where space (for fittings) is limited and/or in situations that simply will not accommodate rigid pipe. Constructed of high-quality materials, it is mildew resistant. We do not recommend installations in continual sunlight. The black color prevents sunlight penetration which reduces the ability for algae to grow, and makes it practically invisible underwater. It makes a great replacement for rigid pipe or for standard vinyl tubing, and is non-toxic and will not harm fish or plants. A rigid external PVC spiral (helix) resists crushing and impact issues, and provides strength and flexibility required in a variety of pond and water-gardening applications like connecting pumps, filters, waterfalls, sterilizers, drains and filters. It can also be used as a light-duty conduit for running protected cable, phone or fiber optic lines. Our UL non-kink flexible PVC hose is easy and economical enough for almost anyone to use. Trimming or cutting is much simpler than with rigid PVC pipe (it can be cut with PVC pipe cutters, a standard hack saw, a carpenters saw, etc.) It eliminates back-pressure caused by sharp turns created by multiple fittings, which increases the efficiency of your system and lowers your overall operating/energy cost. Each fitting eliminated with this highly-flexible pipe is one less fitting that can fail and cause your system to leak. The smooth interior reduces friction, increasing your efficiency and lowering your overall operating cost. It also coils easily for storage and transport. It is specifically designed for use in the installation and maintenance of water gardens, koi ponds, waterfalls, fountains, aquariums and fish hatcheries, drains, light farming and gardening, light irrigation and other similar water transfer applications where flexibility and ease of use is demanded.