Bat Rings

Porzana manufactures special lipped bat rings which have been designed to minimise the risk of damage to the bat’s wing membrane, which is known to occur when standard split bird rings are fitted. The rings are made either of a soft aluminium/magnesium alloy or of the harder and more durable incoloy (a nickel-chromium alloy). The rings are made on hand-presses and care is taken at each manufacturing stage to ensure all sharp edges are removed.

There are five sizes of alloy rings (2.4, 2.9, 4.2, 5.2 and 6.5 mm), and both the 2.4 and 2.9 mm sizes are made in either 4.0 mm or 5.5 mm wide material. The incoloy rings are made in three sizes (2.8, 3.5 and 5.2 mm). The table below gives full details of the products we manufacture. Although the rings are produced on a round mandrel, they become slightly oval shaped when closed. The sizes listed below are across the width of the oval at its widest part when the gap is closed to 1.0 mm, but the shape and size of the closed ring will vary according to the closing method adopted.

Approx internal width when gap closed to 1 mm Metal Height & Gauge Rings per packet
2.4 mm (narrow) 4.0 x 0.38 mm 50
2.4 mm (wide) 5.5 x 0.38 mm 50
2.9 mm (narrow) 4.0 x 0.38 mm 50
2.9 mm (wide) 5.5 x 0.38 mm 50
4.2 mm 5.5 x 0.50 mm 50
5.2 mm 5.5 x 0.50 mm 50
6.5 mm 7.0 x 0.60 mm 50


Approx internal width when gap closed to 1 mm Metal Height & Gauge Rings per packet
2.8 mm 5.5 x 0.35 mm 50
3.5 mm 5.5 x 0.35 mm 50
5.2 mm 5.5 x 0.35 mm 50


Addresses and Numbering

Many customers require just a simple number on the rings, whilst others also require an address. The amount of information that can be stamped on a ring is dependent on the size of the ring, and the table below describes the limits. For example, a 2.4 mm ring can have a one line address with a maximum of nine characters plus a six digit number. Typically the number will comprise of a one or two character prefix and then the number (e.g. A00001 or AB0001). It should be emphasised that these are the maximum characters and numbers that can be shown on the ring, and for clarity it is advisable to keep the address and numbering system as simple as possible.

Address die Numerator
Approx internal width when gap closed to 1mm Metal Height Max Lines Max Characters Max Height Number Size Max Digits
2.4mm 4.0 & 5.5 mm 1 9 1.0 1.5 6
2.9 mm to 4.2 mm 4.0 & 5.5 mm 1 10 1.0 1.5 7
5.2 mm to 6.5 mm 5.5 & 7.0 mm 1 13 1.3 1.6 7
If an address is required then a unique address die needs to be made, and this will then be retained at the factory for future orders. If large numbers of rings are to be made and the wording on the address varies by size then it will be necessary to have more than one die made, although for most customers one address die will be suitable to cover all sizes. The manufacture of address dies has to be subcontracted to a specialist engraving company but a quotation for the cost of producing these dies can be obtained on request.