What yarn is recommended to use with the 15 mm (P/Q) crochet hook?

It is recommended that "Weight 7 - Jumbo" yarn weights are used with the 15 mm (P/Q) crochet hook size.

What is the comparable UK size of a P/Q-19 crochet hook?

The United Kingdom size of - is the same as the US crochet hook size of P/Q-19.

The metric size of 15 mm is the same as the US crochet hook size of P/Q-19.

The US size of P/Q-19 is the same as the metric crochet hook size of 15 mm.

US Name:	P/Q-19
UK Name:	-
Metric Name:	15 mm
Yarn Weight:	This crochet hook size works well when paired with the following yarn weight(s). Jumbo Weight #7: Jumbo and Roving

These free crochet patterns were all created using various yarn types and brands, but all use the 15 mm (P/Q) sized crochet hook.