13mm piping description is further down the description.

4mm(ID) 6mm(OD) Micro Irrigation Flexible Tube/ Tubing/ Pipe Hozelock compatible

This micro irrigation pipe is durable and flexible. The declared size of 4mm internal and 6mm external diameter may vary slightly due to the manufacturing process, however, this variation would not make any significant difference to the use of the piping. If you are having a difficulty getting fixtures into the pipe please gently warm the pipe in hot water.

Product Features:
1. Made from environmental-friendly materials
2. Aging resistance
3. Non-toxic and odorless
4. Functions: agriculture, lawn, garden and industrial irrigation hoses;

Parameters:
1. Material:  Plastic
2. Weight: a roll of about 430/1065 grams
3. Size:
(1) Internal diameter: about 4mm / 0.16in;
(2) External diameter: about 7mm / 0.28in,
(3) Length: about 20m /787.4in, 50m / 1968.5in
(4) Color: Black

Instructions:
1. Directly insert it; boiled water can be used to soak it if it is too hard at the beginning; it is easier to be inserted after it gets softened.
2. Note: only suitable for hose about 4/7mm ( 0.16/0.28in )

13mm(ID) 16mm(OD) Micro Irrigation Flexible Tube/ Tubing/ Pipe Hozelock compatible

Black LDPE Water Pipe 4 Bar Rated Made In The EU 

Low-Density Polyethylene pipe is a thin walled water pipe that is suitable for domestic and commercial irrigation systems.  The pipe is made in Holland to a very high standard by Netafim who is one of the World leading irrigation component manufacturers.  The pipe is flexible, UV stabilised and will resist damage from frost during the winter months when drained.  The pipe can be installed on the surface or just below the surface.  LDPE pipe is not suitable for deep installation.  For pipe that is to be installed at depth please see our MDPE listing.  The pipe can be used to carry water to animal feed troughs, pheasant pens, and many other applications.  It should not be used for human drinking water.  

LDPE pipe is very suitable for DIY Solar heating systems for outdoor swimming pools as it absorbs heat easily.  

It can be punctured with any of the holes punches available from the major retail watering systems suppliers who's name begins with H or a G or a C.  Once punctured you can insert any of their sprayers or drippers.  

We supply LDPE pipe in 4 diameters For advice on the most suitable diameter call or email and explain what you are doing and we will always give advice

13mm inside diameter.  This is the same as 16mm outside diameter pipe, however, most people will search for 13mm inside diameter 
1/2" Inside diameter.  Again this is the same as 16 mm outside diameter 
Postage Policy: 
I only post using Royal Mail or a tracked courier service. Both free of charge for the UK. All postage is quick. Same day dispatch most days.
Please eBay message or call us if you have any questions. We will happily answer any questions you may have and assure you of our best customer service at all times.
.
UK VAT Registered Seller GB 255 9569 54

Free UK Delivery! UK VAT Registered Seller! GB 255 9569 54
◥◤ Free & Fast Same day Dispatch ◥◤ 12 Month Warranty ◥◤