The upcoming Singapore Squash Open will include, for the first time, two Squash 57 events for men and women aged 40 and above.

Formerly known as racquetball, Squash 57 is played with a larger ball - which has a maximum diameter of 57mm, compared to 40mm for a squash ball - and a shorter racket, and "is a popular introduction to squash and can keep generations of players fit and active, and playing on court well into later years", according to a write-up on the World Squash Federation website.

The two new events will be among 10 offered in the tournament, to be held at the Kallang Squash Centre from Dec 5 to 10.

The men's Squash 57 competition will be headlined by local great Zainal Abidin, while Cecilia Lee heads the women's Squash 57 event.

The tournament will also feature the Professional Squash Association (PSA) Men's Challenger 5 event, which has attracted participants from nine teams - hosts Singapore, Malaysia, Hong Kong, Chinese Taipei, India, Australia, Thailand, Philippines and Pakistan, while participants from Zimbabwe and Scotland are in the reserve list.

Hong Kong's Henry Leung and Chris Lo, and Malaysia's Valentino Bong and Elvinn Keo are the top four seeds in this event, which also features Singapore's Vivian Rhamanan and Chua Man Chin.

In addition, six other Singaporeans, including SEA Games men's team gold medallists Samuel Kang, Pang Ka Hoe and Benedict Chan, will play in the Men's Challenger 5 qualifiers.