Hallprint now specialises in the development of customised anchoring systems for use with pop-up satellite tags. These can also be customised for a range of acoustic and radio tags. There are two basic stainless steel head designs and sizes available, the stainless steel medium darts (SSMD) and the stainless steel large darts (SSLD). These can be coated with polethylene to assist in tissue adhesion. A further option preferred by some researchers is the large nylon "umbrella" heads developed by Michael Domeier in the USA. These are attached to high breaking strain stainless swivels using 7 strand stainless wire or 2.0 mm monofilament crimped at either end. A completely print protected "tether tube" has been developed to cover the tether wire or monofilament.